latest Creative Labs sound cards - X-Fi should be your choice - cheapest variation is Extreme music as far as i remember and it should be available around $100-120
X-Fi's are 8 channel ones (7.1 and can be used for smaller configurations too). 7.1 configurations use 4 cables as usual. I think good sound card is important cause some games really die no matter what is your PC if sound card is using your processor to calculate evrything.