1) HDMI only supports 2 channels audio (wtf!)
2) Using an optical cable I can't really get 5.1 sound to work (more explained below)
As for #2, when I play a movie from iTunes which states its in 5.1 sound it only outputs in 2 channel. If i go into the sound devices control panel and "Test Dolby Digital" it does output 5.1 on my receiver. Maybe this is a driver problem?
Would I be better off just getting a new HD/audio card and disabling the onboard crap?
Any opinions would be welcome. This was a first time build.
Don't know about the HDMI problem, but the optical issue is one that gets many people:
the only way optical can transmit 5.1 is using Dolby Digital/DTS; normal 5.1 audio is too large to be carried via SPDIF. As such, unless you have a dedicated soundcard to encode all audio to one of those two formats, the best you can get with SPDIF is 2.0.
As for DVD's, they should already have a 5.1 Dolby Digital/DTS track, so you can still get 5.1 without a soundcard by making sure the source audio is sent to you're reciever PRIOR to being decoded (most movie playback software on the PC tends to have software decoders built in). Its mainly for games that you need a soundcard/encoder combo to get 5.1 over a SPDIF connection.
As for the HDMI, remember, even if you can transmit 7.1, if the source is 2.0, thats all that will get sent. Make sure you are using a 7.1/5.1 source when using the HDMI connection, and try again.