I don't know anything about your M-Audio card, so there's not a lot I can offer about how it's DAC would compare to the 990. The USB connection (which would bypass the sound card entirely) supports PCM stereo only, but with WAV, FLAC, and MP3 sources that would work fine. How far away is the computer from the 990? That might be a significant factor: USB has a limit on supported cable length and long analog cables offer an opportunity for interference if run near other wiring, but optical digital audio cables would have no problem with long cable runs.