installing an aftermarket cd receiver( but with no cd, since its broken so i gutted it, just using it for the tv, radio, 80x4 receiver, and digital media

where is the factory amp located?
wired my harness to radio for power and everything else, except just for the speaker wires, so now i know that they are connected to the amp?
so do i cut wires and connect to aftermarket or should i just splice, doing that it will connect thru both stock amp and aftermarket receiver

etc info- got the metra kit, tried getting a adapter for the line output and to go to the speakers but that didnt work