Just for clarification here the XDA will accept 24/192 via USB with no issues provided your computer will send that out. Eric had to download some third party software to get his computer to port out 24/192 but once he did the XDA picked right up on it and ran with no issues.
For question number 2 I would say no. I realize there is a lot of varying opinions out there on the subject. In both systems that I have tried the XDA-1, I seem to prefer USB connection. This is not the case with another DAC of mine though. Really, the best way is to try it in your own system. Just because I like one over the other does not mean you will have the same results with your system and listening tastes. If the USB is keeping you from buying the unit, don't let it. Buy it with confidence that the USB can produce some quality sound.
Speakers: Monitor Audio RS8's, RSLCR, RSFX
Subs: Dual Epik Empires
Powered by: Dual XPA-5's & XMC-1
TV: Samsung 52" A750
Sources: Pio Elite BDP-05fd, Toshiba HD-A30, DirecTV HD, HTPC
Extras: Music Hall 25.2 DAC, JoLida JD9, Panamax 5100 (x2), Roku
Thanks guys. I appreciate the input. I hadn't seen that quote from Lonnie. I thought there was still some doubt as to weather the USB input supported the same specs as the other inputs. Glad to see that it does. I'm looking at the vortexbox and it only has USB output.