Why don't you trust the quality of downloaded music? It's really easy to check if a file has completed without errors, and what the bit rate is. Also, real audio fanatics wouldn't even be satisfied with CD-quality audio :p, and would gag at the thought of compressed audio, even at 320kbps.

Personally, I'm satisfied with 224kbps MP3 and higher, and I have little problems finding music in that quality online.