Plugging Audigy 2 to a digital receiver

[Laslo]

I am looking for the most optimized setup while keeping my computer speakers hooked up. I know squat when it comes to sound card specifics so I need input from my favourite circle to help me out before I start spending money on special cables. My souncard is just an Audigy 2 with only bare drivers installed and the receiver is a 6.1 Onkyo TXDS-797 receiver. For awhile I have plugged the sound card to the receiver from the line 1 jack to the receiver video RCA inputs -but the vol. from the receiver is almost at half volume. And using the splitter really sucks in splitting the computer and receiver signal. I know the soundcard has a digital out but I had heard that it only works for Creative digital speakers. If that is not true, can anybody point to me on where the choice cables are and type to use?