I finally hooked up the Bel Canto to my computer via optical, instead of the usual USB.  (Behold the awesome power of procrastination ).  Not sure if its any better.  I put on a Fleet Foxes song and heard some distortion I never noticed before, but too much for me to have simply overlooked it.  Maybe the Bel Canto Dac3 has a crappy optical implementation, or maybe my 680i mobo does.  I don't hear anything objectionable w/ the Living Stereo classical I've been ripping today though.  I get the feeling I've lost some texture in the violins, but maybe its just not as 'warm' as usual w/ my HD650s.  Then again, its picking up amazing texture from what I think is an oboe.  Could I really have been that deaf w/ the USB setup I've had for so long  
 
Also the Oppo Digital redbook has sounded fine to the Bel Canto via optical.   
 
I'll need to do more listening this week, I guess.  Though I may move my 'big rig' back up to my room to use w/ my new computer.