For me its:
1) SB Audigy
2) Feeds into mid-90's Kenwood PL receiver and then into my JBL S-312's.
This situation is way overkill (for a PC that is) and more a result of space considerations and family considerations for the time being.
Funnily enough Thor, I have found myself listening to more MP3's in the last month than vinyl or CD!
As for that AOpen mobo, its a novel concept, but you'd need a heck of a well ventilated case to run it. Cooling is an issue anyway these days, without throwing a HOT tube in there for good measure too.
I would love to hear it just for interests' sake.