ok i have a 94 sc400 its got a either 6 dis or 12 dis player that does not work is there a way to test this or can it be sold what kinda spearkers are in this car and also the rear sub is notworking is that because maybe the factory amp has went out?// and also im gonna put 2 12 in subs how do i by pass the factory amp cause im guessing its no good