pioneer gm d7400m

I installed a GM-D7400M with sub from same brand, my car is a chevy cavalier 98. I used a 8 Gauge wire. Sub wired in 2 ohms 400 RMS. If i play music too high with a big bass sound the sub stop and come back.. as i can see there is lack of power. What is the best thing to day? Changing the wire? I dont think the Big3 will do a difference because the amp got only 50A.

The Big Three can help (not fix...) in nearly any install. This is not your entire issue, though. Your issue lies with the fact that your alternator is too small, and you have installed more accessory than the stock electrical system was ever meant to handle. You MUST upgrade your alternator, the source of all the electrical power in the car.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."