The newer Creative products are mostly fine now with Windows 7, based on my experience at least. If memory serves, you won't get the 5.1 if you aren't feeding the MixAmp a Dolby Digital signal... which I don't think your motherboard is capable of producing.
There are a number of sound cards on the market today which will provide a DD output:
Creative X-Fi Titanium
Auzentech (including X-Fi Forte)
Asus Xonar (incluidng DX, D2, ST/STX)
HT Omega (I'm not sure which ones, not very familiar with the brand)
EAX itself is sort of a moot point since Windows Vista/7 changed the way sound cards handle audio. The X-Fi based cards above, though, can use the Creative ALchemy program to conver EAX audio effects to OpenAL, and some of the Asus cards can do something similar (though it's iffy at best, IMHO). That said, all the cards above should provide you with good 5.1 positional audio over optical using DD.
Im in the exact same situation as Rooslin with my A40s and P6T DeluxV2. I use my pc for gaming mostly, but listen to alot of tunes and watch a fair amount of BluRay/DVD movies. I've been thinkin hard on the Asus Xonar STX but read a few reviews picking it apart when it comes to gaming. Is that just on their "benchs" or tests? I'm thinkin its such an impressive piece of equip. that it'd prb be fine, but I'm far from knowledgable on the subject. Any advice would be appreciated.