How can I fix my subwoofer system in my car?

I have the power, remote turn-on, ground, RCA hookups, and speakers wires all hooked up in my car. All the wires have power and work, and I have tried 4 different amplifiers in my car. The first one I had worked, but then it got broke. Now none of them work. The amplifiers show no power and won't send to my subwoofer. What can I do?