Hey there @Bongo Welcome to hifiguides,
Perhaps I can offer some information and advice on this one!
I wanted to start here as this is rather important to touch on before anything else. This was one of my first headphones I bought for gaming and while I myself enjoyed them, greatly so and still have them, they are definitely not for everyone. The reason for this is simply put the treble. The dt990s have some of the sharpest treble I have ever sat down with and if you have any form of treble sensitivity this will definitely tell you, by scratching it out of your ears. It can be found horrifically sibilant without someone who can stand that brightness as well as pair it to a respective amp that can drive it while reigning that treble in. While you can also get a filter that will drop the peakyness from solderdude over at diyheaven or even remove the pad and place some 1-4 ply toilet paper cut to size behind its foam on the driver, and it will decrease the treble dramatically, this headphone is rather I wanna say a hit or miss. I would highly recommend auditioning this one if you feel it may be worth to you and not fully commit to its purchase just incase. If you have an audio store or a place with a return policy that would be best here. Also, the headphone sounds its best and more refined in it’s 600 ohm “edition” which will demand an amp around the $100 margin unfortunately. Beyerdynamics are amazing headphones but their housesound is the brighter frequencies of V or U shaped and in some cases Neutral Bright. The sound signature here with the DT 990 is a very sharp V signature or rather a lot of bass and rumble recessed mids(vocals) and a whole lot of brightness(treble).
You do realize the astro A40 is an open backed gaming headset right? lol it’s one of the very few that are actually open backed. It’s not closed. Just some food for thought on that one. If you enjoy the nature of that astro and you found it comfortable you will probably be just fine with open backs.
Right so lets talk mics here for a minute before getting into headphones and dac/amps. So, I had to ask some stuff about microphones when I was first creating my setup as well as I seen you liked my thread so I assume you read through it. The modmics are fine and sound relatively okay with the wireless being incredibly expensive but a hands free option which is nice. You typically have a few options here. Modmic(uni, Usb, Wireless), V-moda Boom Pro 3.5mm and its 2.5mm cousins, some brands have created other 3.5mm boom mics as well now, an external mic whether it be USB or XLR in either condensor or dynamic, or a Lavalier mic which is a small mic that can attach to your shirt.
Typically if your headphone has a detachable cable the cheapest option would just be the v moda or 2.5mm unless its duel sided or a different connector. However, in terms of vocal clarity you will stand to gain the best benefit from the actual xlr or usb microphones. The decision would fall on you as to which microphone you feel most comfortable with using.
You don’t have to particularly go straight for a 650. Sennheisers in generally are relatively neutral and very well rounded. However, I will tell you to immediately skip this one as you mentioned you prefer a wide soundstage. The Sennheisers generally don’t have a really large soundstage and in the case of the 600 series they have a very small stage to them. If you want a sennheiser with the moderate staging you will want the 500 series instead. The ones in the 500 series however have different tuning between one another which will require looking into based on your preferences. If you want the best quality of sound however I would probably say 58x Jubilee if you can get your hands on it as this is one that has the perk of being used with balanced cables for a balanced input amp/dac much like the 600 series. The rest of the 500 series uses a 2.5mm detachable cable and can make use of 2.5mm boom mics if need be. They can be pad swapped too if you want and you can get an ease of access 3d printed ring from modhouse if you feel you want different pads as sennheiser pads tend to be very shallow and relatively small so not the best for someone with very large ears in some cases. Just remember that changing your pads will change a headphones sound in some cases drastically.
Alright so, let’s get started here on some more fun sounding headphones yeah?
Fidelio X2HR: Big brother to the shp9500 very bassy slightly muddy relatively neutral mids and slightly elevated highs. Sounds very smooth and has a incredibly wide sound to it. You can also just get the shp9500 and mod the hell out of it for about a total cost of $120 as well if you prefer that route and you will have more sound choices but you will have to pick up a variety of pads in that regard. Both headphones use a 3.5mm detachable cable allowing access to v-moda boom pro(sounds better than modmics and is cheaper) as well as a 3.5mm bluetooth adapter if you still want to use a modmic allowing it to be converted into a wireless gaming headset. Generally the fidelio x2hr here can be found from $90 - $120. However, the price may drop further as the fidelio X3 is now being released alongside the SHP9600 though they are only in china as of this moment. These headphones should be able to be driven off your current amp/dac combo you have now.
Sennheisers HD558 / HD 598 / 58x Jubilee: these are the ones I feel most worth mentioning. HD 558 has more bass than the others and still maintains a relative neutrality to its sound which is quite nice. It shares the same qualitys in soundstage as the HD 598 and other 500 series. HD 598 this is very balanced out in sound and has a larger soundstage than the 58x jubilee as is customary of the 500 series. 58x Jubilee this one sounds the best and can be balanced while still maintaining a relatively neutral approach. Highly recommended looking into these headphones and their subtle differences. You can pair the 58x Jubilee to an IFI ZEN DAC for a balanced port amp/dac combo otherwise if you pick the other sennheisers they should run fine off your current amp/dac. You should be able to find these headphones from $100 - $200
Beyerdynamic DT series and Gaming series: (all these are maximum $200) This is a bit of a gamble and will depend on you personally. Beyers house sound is that of a bright frequency like mentioned previously however if you can manage it they are one hell of a brand and build quality is that of a tank with extreme comfort and breathable pads. We covered the dt 990 however I wanted to remark that its not a bad headphone at all just not for everyone but lets talk about its cousins in the DT series. DT 880: this is the happy medium of the 3 in this series Neutral Bright with treble raised but not very sharp very neutral mids with beautiful vocals however lacks in sub bass and body and doesn’t sound very full overall. Unlike other sennheisers 880 appears to be more mid centric instead of the regular V signatures and is very well rounded for a lot of people this headphone is just perfection to them as the bass while relatively light is still very natural sounding this headphone is Semi open back while the 990 is open backed and the one I will go into now is closed backed the DT 770. So the dt 770 is a closed back yet still having a relatively wide sound to it despite it being enclosed. It has more of a U shaped signature but still can be seen as a V to some depending on the pad of choice. Since its a closed back and it make fantastic use of Sheepskin or leather based pads. To some this headphone can be seen as very sibilant and like the 990 it will depend on you and your sensitivity. This headphone is not as bright as the 990s but a bit brighter than that of the 880. Now that we covered these three let me explain something a bit more into the ohm factor on these three as if you go to buy one youll notice they have difference impedance levels. Ohms are going to determine its sound and how strong of an amp you need to drive it. The higher the ohm the better and more refined these will sound. DT 770’s highest was 250 ohm however 80 ohms sound fine to a lot of people. DT 880 bar none sounds its best in 600 ohms but can get away in some cases with its 80 and 250 ohms and 990 I very highly recommend only using this in 600 ohms as its much peakier in 250 ohms unless you can manage it. You will generally need a stronger amp to drive these. Something to note is that you can also have these modded to have a detachable cable or balanced. DT 880 will sound better on tube amps and help with the low end and recommended to pair the other two to a combo unit such as IFI ZEN DAC combo SCHIIT HEL or Seperate unit Monoprice Liquid Spark + Topping D10 to start out with. These will run the 600 ohms and bring in the treble.
Game series of beyerdynamic: So one of the things that beyerdynamic has done is that they realized not everyone is a big fan of brighter headphones so they developed a “Custom” series as well as gaming headphones. Let’s start at my favorite known as the Tygr 300R unlike the rest of the beyers this is like a retuned 990 it maintains a lot of bass but not overwhelming instead of very recessed mids it now maintains a more neutral approach and now instead of brightness it goes dark with an ever so slight brightness peak to it. Very wide large soundstage very warm and one of the most comfortable beyerdynamics I have worn that practically disappears off the head, this ones to the point I refuse to get rid of it. You can relay to my total review on this headphone over here 🔶 Beyerdynamic TYGR 300 R - #303 by Falenkor after that you have the mmx300. This is a headphone that is very siimlar to the dt series but its actually a gaming headset now and doesn’t require amplification, also tygr doesn’t either but it helps. MMX300 sounds very wide and not as bright in comparison and has been compared to the ARGONs from modhouse it sounds great but a lot have agreed that its rather too expensive for what it is nonetheless its quite the fantastic headset and worth mentioning. Lastly, the custom one Pro plus this is an adaptable headphone with a wire mic and adjustable bass slider allowing the signature to change. The bass will dramatically increase based on the settings of the headphones slider mids fall on neutral and treble falls on dark or neutral its for those who generally like the sound of the dt 770 but just don’t like the brightness yet also want a more customizable approach. Your syba should be able to drive the game based series just fine
T50RP and its respective Mods: This is the base form to the incredible headphone known as Modhouse Argons. Modders favorite and can be adjusted to pretty much whatever sound you want. Base form of t50 rp is around $150. Demands a pad swap and depending on the pad you can completely change the sound signature here to pretty much whatever you want as each pad will change it dfiferently. Bit of a fun approach to getting into audiophile gear. However, definitely requires a strong amp in the $100 range. You can of course obtain an argon outright but these are around $350 + and will take several weeks to obtain. The other great alternative is Dekoni Blue which has already some great pads that allow for a V signature and has some modifications added to the headphone these can actually sometimes be found at the same or even cheaper pricing than the base form. This headphone is fantastic for someone who just wants an extreme amount of versatility and wide access to signatures. It’s a planar too so that bass slam and speed is definitely noticeable as is customary of a planar. Semi Open back but can be modified to be fully closed or fully open as well.
Audio Technica M40x: While in my guide I would recommend a ad—x series here in this case the m40x is more laid back. This absolutey demands a good pad swap as the pads on this one are just garbage though the headphone is cheap and portable as well. Using certain pads can open up its soundstage quite well for a closed back. I have seen many recommend cowhide pads for the best signature here. 2.5mm detachable cable. Worth taking a look. Doesn’t need an amp particularly but it can run fine off your syba.
Meze 99 series: Classic, Neo, Noir. Great headphones very warm and smooth with a moderate level of soundstage to them. Luxurious and to some people just look beautiful with their wooden finish. Relaxing sound that while not the best in gaming just for regular music and listening are awesome. Responds well to pad swaps. Uses duel sided cables. Classic is the most expensive while the other two versions are $200. Does well with an amp.
Hifiman Sundara: neutral bright. duel sided cables and can be balanced accordingly. Build quality is relatively decent. Company has quality control issues. Planar and has the speed and slam accordingly. Very detailed with a natural sound to it. Very open and wide. Can be found around $250 mark.
(in used yet good condition only) Beyerdynamic Premium DT series 1990 / T1 / 1770 / 177x GO: These are the next step up from the original beyers and have a more refinement to their treble so its not so bothersome. DT 1990(250 ohms only) isn’t the greatest for relaxed listening but it is one hell of a competitor it sounds great very analytical with 3 different sound signatures though very aggressive can sound like a 770 880 or 990 depending on the pads but with more refinement and detail. T1 gen 2 demands a powerful amp and can be balanced as this one is in 600 ohms relaxing bassy mids sound recessed but are still up in the mix with raised treble rounded bass with a very wide presentation this headphone just sounds great and feels great. 1770 had some issues here and thing with quality control but is a step up from the 770s still the same signature just more refined and now has better cables 4 pin mini xlr allowing balanced connections. 177x Go is the more refined version of the 1770 more towards neutral yet still bass and treble increased with mids now being more neutral lower ohms so its portable and still maintaining the ability to be balanced. All of these have a large soundstage, dt 1990 is the only one that cannot be balanced, T1 has some of the most progressive sound depending on how good of an amp you have. I mention to buy these in used as right now they are found in the $500+ range sometimes $600 however, from time to time you will find them being sold around $300 - $450 which if found allows these to be placed in this list.
Dac/amps will depend on what your going after. I would suggest figuring which headphone is best for you before deciding on this one as it will also tell you how much budget you have left for this.