My recommendation is an old JBL D130F. It was originally a speaker built by James B. Lansing for Fender (hence the F) because Dick Dale wanted something that could take 100W from a tube head amp. The speaker dates back to c.1956-1958. I just aquired one from a friend and had it re-voiced and coned. It was $215 to do from JBL but worth the effort. I then proceeded to build a box, I know what you are thinking...rest assured, it is awesome! Quite possibly one the the cleanest sounding speakers, especially for a sub, I have ever heard. I am driving it with 150W currently, but looking for my own amp since the one I have isn't mine. It was broken (that is why I had the work done) while being driven with 1000W in a chain of three...it can take the punishment!!! Anyways, usually you can find one of these speakers between $100-$350 depending on its condition. If you need any other advice on this particular speaker, let me know! yosemitesamiam@yahoo.com