Here are a couple posts I made about the RME ADI-2 that may assist you in getting a better idea of why/how that particular purchase ended the audio-upgrade game for me. The first one goes into detail about my experience buying the unit and where/how i got it.
This second post in the same thread, talks about the two schools of thought when it comes to audio equipment. It is also applicable when talking about how that unit ‘sounds’.