I am a non audiophile but want to learn a bit. For this scenario I have a home theater pc using HDMI audio to my big screen and I am just using my big screen speakers. I would like to use the PC for a receiver as well by installing a dedicated sound card that will take the spdif optical signal from my big screen and then output that to a set of klipsch 5.1 promedia speakers I have that only has the three 3.5mm jacks for left/right, surround, and center/sub. Does this make sense at all and if so it is possible with any sound card out there?
Some newer PC speakers have better digital connectivity, however none will hold a candle to the sound quality you get from the klipsch 5.1 promedia speakers. So do yourself a favor and don't go that route. Stick with your current speakers and the above suggestion and you will have a better sounding system.