lol I was in your same boat like two weeks ago bro. I know exactly what you need.
http://www.etronics.com/product.asp?State=WI&showship=ok&stk_code=tecmb3000That is what I got and I have it running two Diamond D6s right now like its nothing.
You will also need to buy several spliter cables. One to split your audio out of your computer into a right and left channel then split the right and left channels again. Its kind of confusing and Im terrible at giving directions but from there you should have two right channels and two left channels.
Plug one left and one right into this amp and the other right and left into your home reciever. This way you have one amp running your speakers and one running your subs.
I'm sure there are other ways to go about this but it is the easiest way I found and the most cost effective. I can shake half the dorms with these subs when I want but at normal bass my 5.2 setup sounds kick *** during movies and video games.