I'm actually in the same boat you are in right now. I posted something similar just a few days ago. I've looked into the Velodyne VX-10 which I've heard is a great sub for the price (around $175 shipped). If you are willing to wait and save up some more, I've been recommended to try the BIC Acoustech H-100 which runs about $275 shipped. I've got the BIC Acoustech front and center speakers, so I've debated which route i truely want to go.