RaT, if I read mike c's post correctly it is only $100 for replacement surrounds. If you're happy with the sub, that sounds pretty affordable to me. Of course you can never really go wrong with having two subs. I'd probably get the bigger badder beast and fix the old one, then use them both.
When I upgraded my sub, I kept my old one and use them both. I like it much more than having just one sub. Then, if I'm watching movies late at night, I can just turn the bigger one off and still enjoy movies without p!ssing off my neighbors too much.
Jack