I'm in the same situation, but with Supreme FX-II that comes with Asus Rampage Formula. Worked just great with Win XP Prof x86. I've now tested a lot of drivers
with this and with every one of them the sound comes from the rear speakers while testing, but when I try to play music with winamp or watch videos with VLC the rear speakers won't work.
I'd appreciate some help also.
Ps. I think of trying to install the old drivers in compatibility mode. Will tell if I get lucky.