If you're stuck with optical or coaxial SPDIF, then the only way to get 5.1 is through compressed audio, in which case DD Live would work well. PCM will be only 2 channels.
With HDMI, you no longer have that issue because new video cards can send out 7.1 uncompressed channels to your receiver.
Antec NSK-1480: stock i5 2400 @ 1.04v, 4x4GB Mushkin Silverline, 160GB X25-M G2, Dell U2412M + U2211H
Lian-Li A04: stock Q8200 @ 0.98125v, 2x2GB Mushkin Silverline, 80GB X25-M G1, 1+1.5TB Caviar Green, 2x3TB Caviar Red, 1.5+2TB+3TB Barracuda, 1GB HD 5750 (passive), Sony BWU-100A BD-RE, all on Seasonic X460, hooked up to Sony 40" EX620 + KEF 2005.3 + Yamaha RX-V667