I currently am looking to buy an amp for my soon-to-be-owned sennheiser 660s, and I"m currently at a bit of a crossroads.
Since my 660s are probably gonna be mostly for music or single-player games, I was thinking of getting an entry-level Schitt Magni 3+/Heresy for a cheap $100. But when I AM gaming I’ll be using a 3.5mm cable with mic (e.g. VModa boompro, Modmic, THX Panda + mic) so I’m also considering whether I should open up my budget and get the Mayflower Arc MkII for $250.
So really what I’m asking is, how big of a difference will an amp (and a DAC i suppose for the mayflower) affect gaming audio? Because if it really isn’t a big difference, I might not limit my options to the Mayflower and just go for a cheap amp. But if the difference is at least noticeable (and in a more competitive sense like hearing footsteps better or smth lke htat) I might just go for Mayflower instead.
All advice appreciated 
@ChiuTrain00 Welcome to HifiGuides,
put simply dacs can change the sound. They add a higher quality sound and also tend to add more detail and clean up the sound as well as in some cases fix distortion and bloat among other things. However, amps offer a much more significant change in the sound unlike dacs which are fairly marginal changes unless you change price tiers drastically. Heres a general list of amp/dacs though that you may find interesting from zeos’s old post
Is there any downsides to running a 1/4 to 3.5mm adapter? I believe that makes it an unbalanced connection right? Are the downsides of unbalanced connections big?
Balanced are particular plugs that are different from the regular 1/4 or 3.5mm. Balanced tend to sound better but it boils down to which headphone as not all headphones are capable of balance or rather not all sound good being balanced and don’t get much benefit. This would require quite the lengthy explaination. To avoid that and typing a giant book you can find most of what your wondering about as far as balance vs unbalanced and the different plugs here Balanced vs Unbalanced Audio Connections | Headphonesty
No downside. Also, this doesn’t “make” an unbalanced connector. Both 3.5mm and 1/4" jacks and plugs are most frequently unbalanced.
I think going with one of the Schiit amps (or an Atom or Liquid Spark) will give you the best sound in the entry-level price range. An outboard DAC will also help improve some of the Spatial recreation for footsteps and such. If you want an audio interface to plug your headphones and mic in to the same box, a Focusrite Scarlet Solo would be a good option. Pair that with a Magni and you’re off and running.
Edit: plugging both mic and cans into same box was poorly stated above. If you go Scarlet Solo + Magni you would plug mic into Solo and headphones into Magni. The Solo would be your headphone dac and give you mic gain control with a knob instead of software.