i would get three of those subs from this buyer on ebay. http://cgi.ebay.com/NEW-RE-AUDIO-SRX15D4-600w-SRX-15-D4-CAR-SUBWOOFER-/300452845042?pt=Car_Subwoofers_Enclosures
and make them in sealed enclosure with about 4.5-5 cubic ft net on the volume and put about 900-1500 rms to the 3 and you should slap like hell and sound good doing it.