it comes with 6 rca cables. you dont need anything else. just make sure your pc's onboard sound/soundcard is compatable and set up correctly for 5.1 surround.
http://www.genius-europe.com/en/produktdetail.php?ID2=49&ID=29&ID3=507
yea i laught when i saw how easy it is i found all cables and made it 5.1 it was no problem it works like a dream