What are some subs that are equal to or greater in performance compared to the Sony SAWM40, but that I may be able to find used or on special for a price that is similar to the SAWM40 (which is about $160)?
Maybe not quite that cheap, but the least expensive yamaha subwoofer is similar in performance, if not a little better. Look for that subwoofer. Check out the yamaha website to see the smallest subwoofer.
The DLS 10 inch sub from Parts Express (part number 300-630) is supposed to be quite a performer for the money. And for only $100 each you could buy 2 and spend only $40 over the Sony. If you're interested then go to the tech talk forum at Parts Express ( Link Removed ) and search for posts on that part number.