"Limp Bizkit - Behind Blue Eye's" has the most killer bass I have ever heard? Total surprise! Also Outkast's "The way you Move" and the New Ludicris Waterfalls song both have nice smooth strong bass.
Yeah on my subwoofer, Ain't no Sunshine Ain't got no bass. But on my friends it gives you a headache. My Sub goes way lower though, like on Rap Bass songs it gets reallly low.
Get that amp or maybe a stronger one and get one 15" Audiobahn Immortal from http://www.cardiscountstereos.com/
Its way cheaper and better then Kicker L7. The sub isn't even designed by Audiobahn!