Sorry to derail the thread with essentially what is a bug report.
After testing and retesting things I have come to think the problem is not with USB 3, since VLC will play audio files without a hitch, but with some update at some point that seems to have done something evil with iTunes and the ODAC. Re-installing iTunes doesn't seem to help, so I am all outta ideas besides the obvious: getting a PC. Heh.
Thanks for everyone trying this out though.