i just bought a gn it needs some bass very badly it has concert sound.i wanted to put eiter 2 10 behind the seat or 4 10's on the rear deck.do i need to keep the 4x10's or just upgrade the front speakers and add a amp. would keeping the insulation on the back seat make me lose bass i dont want to hear the stuff in the trunk and take out the 4x10s let the bass out through the top. i want it to hit hard and clear no trunk rattling or buzzing please help