They are defintly right about the install being a huge part of it. But, to answer your question, i have heard a lot about DD and juggernaut subs on the various boards that i have been on when spl has been mentioned. Something a little more mainstream that is susposed to have great spl are solo barics. But, most of these subs are really loud, but also have terrible sound quality. But, if you just wanna win SPL comps, then that doesnt matter. But, if you are looking for a sub that has high spl but also good SQ, check out some IDMAXs or eclipse titaniums (both of these subs will kill your wallet though). Anyways, hoped this helps. I dont have very much first hand experience with these subs, but they are the main ones that are talking about on a lot of the forums that i go to.