I took a look at the Oppo 83SE manual, and it looks like you can listen to audio files through the USB input. The manual doesn't specify which types of files it'll play, so you may have to experiment. It says it will only play from "USB Mass Storage Class Bulk-Only Transport", but that this includes "[m]ost USB thumbs drives, portable hard disk drives and card readers". Probably won't work from an ipod or other Apple device; it seems like manufacturers have to get a license from Apple to do this, and I don't see any "ipod-ready" notices. I could be wrong, though.
As for whether or not it'll play HD files with HD sound quality, I'm not sure, but I think it will. It's got a very good DAC, that I'm certain can decode 24bit/192khz audio files (sorry, didn't look too closely at specs).
Anyway, you should be able to play from a thumb drive or other external drive via USB, and you should be able to get HD-quality sound, but you may have to experiment a bit with data sources (drives) and file types. I have a cd player that has a USB input, and I love it. I rip into lossless formats (usually ALAC); it sounds great, and it's very convenient - I can leave those damn cds in their cases.
Here's the manual; start at p. 40.
http://download.oppodigital.com/BDP8...ish_Manual.pdf
Good luck!