They both sound the same to my ears. Same chip, similar power, both have a digital volume pot, act as pre-amps, and include a remote. Topping has more inputs including Bluetooth with LDAC and a smaller footprint. The RME has on board EQ, Bass/Treble controls, better build, cool display, and of course a boat load of other extras that I will probably never use…and that Manual…quite a read.
Bottom line is that the price of the DX3 Pro+ is currently $179 (normally $199) and the RME is on sale for $999 (normally $1299).
The only thing that I cannot get with DX3 Pro+ is the loudnesss function of the RME that is an awesome feature. It allows you to listen at low volumes with a fullness that I have not been able to repeat using the APO (Peace) software on my Windows PC.
Am I missing something? Because one has to go back.
Found this online, some measurement about what the loudness does. Might help to rebuild it in APO
Do any DACs apart from RME have equal-loudness features? | Audio Science Review (ASR) Forum
Thing is it seems to be adaptive. The lower the volume the more the bass and highs get boosted. Probably you have to rebuild all the curves (the last 3 are the same actually) and test which one suites your average listening volume the best.
Edit: What is your loudness setting set to? + how many Db (10dB in the picture) and what is your low volume reference point (-20dB in the picture) and then you need to check your listening volume on the RME. If the volume is lower than the reference point the loudness boost is on max. Do you listen above the reference volume the boost gets lower.
The bass boost, for the fullness, looks pretty similar to the ifi xBass. If you like to try that via EQ it’s a low shelf filter +10dB 54Hz 0.5Q
5 times the price is quite a step. Especially when you don’t hear a difference and don’t need the EQ functions. Guess you could better invest that into another pair of headphones.
Thanks that helps. I will try that “+10dB 54Hz 0.5Q” and see what I can do. I have already attempted to put in some eq presets in APO with some success. It is fine until I compare it directly to the RME which is different (and better) but perhaps the ifi setting will help. I have loudness set to +8db on both bass and treble and Low Vol Ref set at -20
You might be on to something. I have good preliminary results inputting the following; 54hz/+12.5db/.5Q and I added 4800hz/+3.14db/.05Q with 16000hz/+7.2db/.001Q to round out the highs (pre-amp set to -2db for now). I like it…thanks.
So, What happened to the RME? It’s still around or got passed on?
Still have both the RME and the DX3 pro+. Lately I picked up some presonus studio monitors and have been running them balanced through the RME and RCA on the Topping. When run in unbalanced you can only use optical otherwise you get noise in the system
I have decided to keep the RME Adi-2 Dac fs. It is just so awesome, especially since I have added monitors. I just saw that Topping released the new L30 and e30, and it. Is going to happen to the pro 3 plus sooner than later. While the Adi 2 has been around for years and they will continue to support it, hopefully. Plus I love ut even if I can only detect minor differences.
I think you made a good choice. I recently bought an RME ADI-2 DAC FS and it is exceptionally good. It lives up to it’s professional audio engineer heritage. Definitely a quality piece of equipment.
2 and a half years later and I am glad that I made that choice. It has been my daily driver with multiple headphones and it has performed perfectly!
It’s actually still in my wishlist on Sweetwater. When I will be able to afford it is another story entirely… 
Had mine about 3.5 years and similar experience. It is just great.
I wouldn’t let go of RME. It’s a small box of wonders!!