I've had an A/V receiver for a while now and have been so far forced to use an optical cable because the soundcard doesn't have an HDMI out. The GPU does, but I can't use that as I have a 3D monitor that doesn't use HDMI. So I've been looking for either an optical or 5.1ch analog (all 5 ports from soundcard, not just Red/White) into HDMI. As I understand it when you use Optical, the PC has to encode the digital sound first before hitting the receiver or you wont get directional sound, while HDMI or Analog does not need to be encoded first.