POS Electrical system in V6 Ls

My battery and brake check lights flicker when I push the accelerator, and my headlights dim when ever the check lights come on. Also, my subwoofer keeps shutting off whenever it hits too hard. I have changed my battery, alternator and terminal fuse. Please help. . .

Is your alternator putting out enough amps? If not, that could be the problem, same if the voltage regulator isn't functioning right, usually the diodes cause ripple.