Xbox 360 5.1 via optical

Hi,

I am in need of some help. I want to connect my 360 via the optical out on my VGA cable in order to get proper 5.1 sound through my Creative Gigaworks g-500 speakers. atm I have an X-fi XtremeMusic which has no optical or decoding capabilities. I recently upgraded to the X-fi titanium fatal1ty card but that does not do hardware decoding so I just RMAd that.

All I can find is the X-fi elite pro but that cost near £200. Is there any cards out there which can do digital to analogue conversion or any cheaper alternatives to the elite pro?

Thanks

Bruce