I am running 330watts rms (165 x 2) and my lights are dimming slightly. I want to know what's the easiest and more importantly the cheapest way to go. I'm not sure if a new battery would do anything, I know a capacitor would not truely fix the problem but it's the cheapest option right now. Also a guy at a car shop up here told me that he got a place to "crank up" his existing alternator by putting more copper on it or something, he said it bumped him up from around 90 amps to 120. Anyone else heard about this method?
Your cheapest solution is to turn the volume down. If you can't do that, then invest in a HO alternator. That is the best solution. Adding a 2nd battery will only give you temp power. After it's discharged, it'll put more strain on your alternator. Depending on your car/make/model, it'll cost as much as a 2nd battery. So it you can afford Optima battery, then you can afford HO alternator. There are some shops that take your old alternator and upgrade it so that you get a bit more juice, ie from 75A to 90A. Don't trust those that claim 120A+. If that was possible, they would charge as much as a HO alternator.