JL Audio 12w7 will pound something fearse but cerwin vega pro stroker duel 2ohm in the right size box will blow your mind. some digital designe also are very good but these subs are very expensive. kicker solo x 18 is very good if you can get enough power to it.

Yes, Solo's, W7's, Power strokers, these are all good, but if you want something to slam hard, this can be different from something that rumbles. This is all about the box. A custom box can swing which output style you get from any sub. I've heard a few small eights that sounded louder, deeper and more full than the average pair of twelves. This was because of the box. A large ported box will give you high effiency, super deep frequency response, and a +3 DB instant improvement over a sealed box with the same amp and sub combo. The only trade off is it isn't a crisp, punchy, and doesn't slam as hard. Putting the same subs into a medium sized sealed box will not be quite as loud, but can give you a concussion it knocks so hard. The boxes to stay away from would be anything isobaric or band-pass. These limit frequency response and give you a minimal output result. These should only be used by someone who doesn't listen to the subs for musical purposes (ie: DB drive competition, just one note for maximum output). This page should explain better what each does. http://www.the12volt.com/caraudio/boxes.asp Figure which output type you want, then buy a decent sub/amp combo, and get a good custom box.