I did the same thing with the door subs. I hooked a Rockford Fosgate PBR300x1 to the Kickers and had the amp mounted where the factory amps used to be. Hits hard enough to make my ears ring. No vibration in the doors yet.
2010 GT Premium, Saleen Series VI.5 w/3.6 pulley, Dynotech DS, Pypes LT, O/R H-pipe, High Flow Cats, Magnaflow Street Axlebacks, Steeda Sports, Koni STR.T, BMR Adj. Panhard, UCA & LCA, Stoptech Stage 2 Slotted Brake Kit, Autometer Boost & A/F gauges, JLT Series 3 CAI, Kenne Bell BAP, CHE K-member Brace, Steeda Battery Relocation Kit, & other supporting mods.