Sound Blaster Surrond 5.1 External USB on Leopard, only 2 channel :(

I hope someone can help me
This is the question, i Have bought a SB surrond 5.1 USB for ADD to my
Macmini G4 1.25 (Leopard 10.5.2) an Optical Output and use 5.1 system
surrond.

This is the product
http://it.europe.creative.com/products/product.asp?category=1&subcategor
y=207&product=15912

Midi setup recognize the SB, and recognize the 6 channel configuration,
but the sound is only STEREO. If I try to test the "center" o
"right/left rear channel" and "Subwoofer" my Home System Surrond are
Mute

A film in DTS plays perfectly by Apple DVD player, but sound are only
Stereo, and using VLC is the same.


I have bought this product because i have read some site that says that
SB LIVE works great on Mac Os X, but SB Live in out of production now,
and the subtistute is SB Surround 5.1 that i think is a little
different.

Any ideas? or i have to bought a M-Audio?

Thanks
Erik

PS
My system surrond is OK, with iMac Intel with integrated optical output
the 5.1 is perfect.