Use that onboard sound, If you are doing a cheap 5.1 setup and don't care about quality. Just follow the instructions on changing the Mic-In jack, In place of a Central, Sub. But this means that you connect a Central Channel or Subwoofer in. So you will have to check for the other 4 speakers. You may only be able to run a Quadrophonic setup depending on how many analog ports you have.