If you don't want the factory amp you can purchase a amp bypass harness that you connect to the head unit and bypasses the factory amp. The harness has RCA type plugs output insted of high level output. Connect RCA plugs from the head unit to your new aftermarket amp. than run the speaker wires to the plug on the old amp (so you don't have to run new wires to all the speakers) and you just saved time. Hope this helps. you can call shellbys car sterio in long beach, ca for the bypass harness.