camaro z28 electrical issues (stereo)

hey guys, i figure i should ask you guys about my problem since camaros and firebirds are quite alike. i am having problems with my car stereo. i have a jbl 1200.1 powering 4 subs and a rockford 400a4 powering speakers, and my alternaotr can not keep everythign charged up. it has a 140 amp alternator in there which makes me wonder whats using up that much power in my car? i dont think that my stereo is that mazssive by any means just good, but i want it to work alot better, i cant even turn it up all the way before the 1200 watt amp cuts out because it cannot get enough power. im planning on buiying a 200+ amp alternator because i think that should solve my problem, but does anyone else have any other suggetsions? thanks

You might need a I believe its called a capacitor(not 100% sure if thats what its called) but it stores up power so when your subs hit it doesn't take all the power from your car. Instead it takes it from the capacitor(?) and then it recharges it when its not used. But, a larger alternator might be a good idea too.