Car Audio Amp Capacitor Help?

I'm confused on Capacitors. Whats the difference in the "FARAD" I see ones from like .2 to like 10. What Capacitor would I need for my system. I have it in a 2004 Grand Prix. I have 2 Alpine Type R's and a Lanzar VIBE286 Viberant 2 Channel 4000 Watts High Power Mosfet Amplifier. The lights dime like hell all the time and the amp shuts off sometimes on deep bass.