Pro-Linear
go to a&bsound and test out this subwoofer
http://www.pro-linear.com/basscube.htm the 10 inch version.
its a 10 inch sealed subwoofer with 400watts dynamic power. FR is 17-200hz, low and high level inputs and outputs.
you can easily get it for 400bucks if you know how to talk to sales men, i usually get 100bucks off everything i buy (cept cables).
if you are not familiar with the brand don't let that discourage you, i have them and i am pleased with there performance.
nothing better for bang per buck.
sheep