Here's my setup that I plan to get:
Speakers: Logitech z506 with 3 3.5mm audio ports for 5.1 sound and 2 RCA ports.
Sound card: Asus Xonar DG with 3 3.5mm audio ports, 1 3.5 audio in port and 1 spdif out.
Video card: Sapphire Radeon 7850 2gb DualX OC edition with hdmi.
PS3. The source of all the problems.
Now I want to hook up my speakers to my computer to get a full 5.1 experience, and use hdmi or spdif for my ps3. Could I use my video card or sound card for such use? Or what other ways could you do it?