The best way is to find a sound card with SPDIF output, typically coaxial cable or fiber-optic. That way you only have one cable to hook up. I have mine set up this way and it works fine. GBPVR will come through as a 2 channel PCM signal from what I remember. So my setup will use the newer ProLogic II while playing sound from GBPVR. When I play DVD's with PowerDVD the receiver switches to Dolby EX mode.
From what I have read you are best to stay away from Creative cards as they are great for gaming but not as good for HTPC use.
AMD Athlon XP 2500+, Asus A7V8X-X, 1 gb Ram, 7600 GT, Hauppauge WinTV-PVR-250 & Hauppauge WinTV-PVR-150, 1.5 Terabyte Seagate HD, XP Pro