I've got an audigy in my rig:
1900xp
ASUS A7V333
512 ddr
Gainward gf4 ti4600 golden sample
SB Audigy
etc,etc,blah,blah
It's still an ok'ish gaming system but i've lost track of the times i've had to fanny about with eax and h/w acceleration settings to get some games to run properly.....so i'd go for the santa cruz m8, i've not heard of many peeps that have probs with the santa cruz..