Your probably drawing an extra 20 to 30 amps over what your stock system was designed for. Even if you had brand new stock power components (engine, alternator, battery, etc.), you still would come up short. So, you need a stronger battery, probably an upgraded altenator and a cap to supplement the bass hits. But, is all this necessary to cure dimming lights? I've never heard of anyone claiming damage from adding a system, but you probably dont have very good overall electrical performance.

Spy