The RME does not need expensive cables, upgraded linear power supply to sound really good. I started stock and it outperformed my Cambridge 851C which is a fairly decent player for the money, which outperforms my Oppo 205 which some are nutty about, but that’s another day. The DAC in my BS Vault 2 is not even worth mentioning, which I ran the Vault through my 851C which was a nice improvement.
What I and others are saying is add a better power supply and it steps up a good notch to a better DAC, actually much better. The RME is good enough that it continues to distinguish the difference between cables and the better the cables, well you guessed it. It is a really good DAC, but that doesn’t mean it’s for everyone, just like someone else may not like a MHDT, Denafrips, Schitt and etc.
No doubt there are better DAC’s but I think ones going to spend much more to really hear much improvement but only differences. I do think that if one gets into the settings and starts messing with tone controls, the EQ and filters one could end up with a sound they do not like and not realize what they did as I agree it is fairly complex to navigate through all its settings at first.
Don’t recall you mentioned what filter you are using.