My home stereo is a 5 speaker set-up (center, 2 main L + R, and 2 sorround) but, I lost sorround sound!?

I know it's not the speakers (I plugged them in where my regular speaker goes and they work.) Any way to fix it would be cool, but it's been actin' funny. So, I'm thinking of replacing it, but can I get just the main unit without the speakers? If so, where?