<font color='#000000'>your not going to get true 6.1 from a stereo source, but you can have a pro-logicII reciever and have it matrix it out to 6 channels.
For your home theater needs the SB Live is a very nice card, but I have heard the Audigy is just better enough to justify it's price.
Since you do a lot of parties, you might want to look for something fairly sensitive. Just make sure you can live with it for casual listening as well. Some rather loud speakers sound bad when they aren't cranked to ten. If they don't let you bring in your own music, you might want to look elsewhere. (as long as it has no offensive lyrics they shouldnt care)Listening to familiar music is the best way to tell a system out.
Also try to have the shop use a receiver similar to yours if possible, sometimes this just can't be done though.
For digital connects, depends on how far the receiver is from the pc...if its fairly close, use coax digital, if its say, downstairs, go optical. Also note that coax digital and audio rca cables are the same, so if you have a spare rca, go for it.
You might want to get some shielded rca cables though, you can get some for cheap, just look around, double shielded is better, any added noise rejection will help ensure your sound is that much cleaner getting to the reciever.</font>