Honestly a sub that is cheap, and doesnt require much space at all, 1.25cu.ft. and hits real damn good, I have 2 of them and am hitting a 139db via TL, would be a 12" Lanzar MAX12D or MAX212D I forget which name they use but that sub pounds hard and doesnt require much space at all. There is this site I use, they have the best prices I have ever seen and carry seriously like every different brands of amps and subs and what not they have low end stuff and high end stuff and everything in between. I have dealt with them for about 5 years now and never once had a problem and recommend them to everyone because they have helped me a ton and everyone that has used them has never had a problem. PM me if you want their site, or email is usually how I do it cause their site they have been working on lately. and they carry everything too underglow, subs, amps, motor stuff.