Oh come on, the splitter would of only be about $3 max
Well, if you have 4.1 capabilities, then it should be rather obvious
Plug the speakers you want for the front output in the front output jack, and rear in the rear output jack... Then find the software for your soundcard and select 4 channel. Some soundcards have mulit purpose outputs(like line in/rear out) Of course you must select what it does.