connecting pc to surround sound system

We've been watching shows in glorious HD for the last week but the sound has been coming through the pc speakers which, for lack of a better term, suck. The sound doesn't do the picture justice so I figure I have to come up with a better sound option. We have a home entertainment system which is right below the tv and used to be connected to the cable box. Unfortunately, the connections arent the same on the pc as the cable box. The pc only has a 3.5mm jack like an ipod does and the surround sound has red and white RCA jacks. A quick search on amazon yielded a 6 ft. RCA to 3.5mm wire for the bargain price of $2.50. I ordered it last night and will hopefully have it in hand early next week. This should complete the whole setup.