I just picked up my Pioneer VSX-84TXSi yesterday after being a month on backorder. Hopefully it doesn't have the LFE problem.
Anyway, to get to one of your questions... From having only an hour or two to fool around with the receiver, I believe that you cannot push one button and have the USB audio and DVI video playing at the same time. You can, I think, push the button for USB audio, then push another button, "video source select" or something like that, which will switch the video source, but not the audio source. If you don't mind all the button mashing, I'm pretty sure it's doable. Haven't tried USB audio, but I did a similar thing with the iPod connection and it worked fine.
