Likely your onboard sound can only output stereo PCM or pre-encoded 5.1 content.
Check in your codec's control software and see if it gives you the option to use DDL (Dolby Digital Live) Encoding or DTS Connect over the S/PDIF.
If it does not, you are probably stuck with stereo unless watching a DVD.
Does the soundcard have to be PCIe?
ASUS just released a new PCI soundcard quite inexpensively that should work just fine for you.
If a standard PCI will work, look into the ASUS Xonar DS for $50.
It supports DTS Interactive Encoding and will be able to output 5.1 surround for everything.
If you must have PCIe, check out the ASUS Xonar DX for $90.
It supports DDL Encoding which will also output full 5.1 surround.
It also has a better DAC and analog output section when compared to the DS.
^^ And the ASUS HDAV1.3, but those cards are really geared toward HTPC systems then anything else...
The only Creative card that makes any sense whatsoever would be the Extremegamer at $40, but its so beaten on sound quality, even by some high-end onboard chipsets, that I don't consider that to be worth the purchase.
hey guys i have a question hope u reply ASAP..i have the same problem as gordan_freemans_t
i have a supremeFX X-fi soundcard that came with my rampage II extreme mobo...when i plugged SPDIF into my LG dvd reciever with an LG 5.1 surround..and into my soundcard..the problem is that my pc isnt playing games and music on 5.1 only dvds..so i think if i buy this thing: http://us.store.creative.com/Home-Theater-Connect-DTS61...
will everything work on 5.1 system btw my pc is reading SPDIF as stereo..or i can simply do a software mod and everythin will work on 5.1 surround?
PLEAS REPLY ASAP ASAP!
sry for bad english