1 - The only INPUTS a sound card will have are Line In & Mic. I think you want OUTPUTS.
2 - You don't need RCA outs, but there are cards that have them. Prepare yourself for sticker shock, though.
3 - The common solution is to use a 3.5mm headphone jack to L/R RCA splitter. A truly clean install would use a cable that has 3.5mm on one end and RCAs on the other.
4 - Time to check out the FAQs. Link in my sig.