Did you go to sound blasters website and get the official drivers? with my Creative X-fi xtreme card i get the control panel aswell so ive got loads of tweaking options, without this the sound is rubbish(well to me it is as im used to it sounding great)
This is what im talking about


With my basic drivers id get sound, even 5.1 but it doesnt sound as good as when ive got the control panel to flick all the goodies on