Well, there are 2 possibilities:
- The Soundblaster Z doesn't feature the hardware acceleration of the X-fi and so can't run properly with X-fi or hardware settings (although I think Creative advertises soundblasters Z still support EAX and OpenAL)
- The Soundblaster Z actually has a software emulation of EAX 5.0 but as usual, they coded their drivers with club-feet and nothing works.
Anyway, if someone wants to buy a soundcard, I would definitively advise him to have a look at the Asus ones.
I've always used Creative ones and I was mostly satisfied (even though there were some problems), but everything since the Recon 3D is twice the price, the hardware acceleration is gone and the sound quality went down.
There's not a single reason anymore to bother with their products (and their crap drivers
)
edit: While I think about it, there might be an easy fix though. Go in the Creative control panel, EAX effects tab. Check that the "EAX effects intensity" slider is at 0 dB. If it's higher it could be the source of your problems.