i was unaware audison was building a couple more dsp's-- i thought that it was a typo at first.... the bit ten lineup looks pretty good...
at the moment, there is only one other documented xoom install:
and his discussion thread:
admittedly, his goals are much less SQ oriented..
unfortunately, there really is not a way to bypass the internal dac's. there is this module that might do the trick, but you could also lose the ability to use the xoom's display, and as it is a untested option, it might not work--so it could be a waste of money for something like this...