ive personally had good luck with this little gem
http://www.newegg.com/app/viewproduc...117-105&DEPA=0
i had my Dell onboard sound and desktop speakers though, so obviously i was blown away when i got that sound card and a set of Logitech Z-640s... but you can get a 5.1 card fore even cheaper than that...you can also get a 7.1 card for a little more if you want to plan for the future..
also i believe that using onboard sound (its where the sound card is sort of embedded in the motherboard and not in a PCI slot) takes up more system resources than using a PCI card..so if you're looking to eek out a bit more performance, thats the way to go.
also as for your card running surround sound i would say it would, even if it only has 3 plugs i think it still can, supposedly you can change what the plug is somehow? a friend of mine did it once, he had 6-channel onboard and it just had the 3 plugs(line in, out, and mic) and he changed the line out and mic to center and rear...but i dont know how.