Help With Surround Sound

I just got a set of 5 Sony speakers and a Sony sub for free but I don't have a receiver.  I want to hook them up to my computer but it's not going to be enough power.  I don't want to go out and buy a $300 receiver for free speakers.  Plus, I don't need all the fancy features and multiple inputs.  Is there any place I can just get an amp or something that's a lot cheaper than a full receiver or what would you suggest?

Disclaimer: I'm definitely not an audiophile and I only understand some of the basics, so if I ask nooby questions I apologize in advance.

Any help will be appreciated.

P.S. Each of the 5 speakers is 140W and the sub is 200W and I think they are all 6 ohm impedance. 

Im sure you could pick up a half decent receiver or amp 2nd hand for dirt cheap. Just make sure its a decent enough brand and its power ouput is adequate enough to feed the speakers.