i have 1 mb quart pwe 354 running at 2 ohms with a raa 1000 amp 500 watts rms and my headlights barely dim even with the amp runnnig at 1 ohm 1000wrms i do have a aftermarket battery and a new alternator probably 100amp i dont know but i do have a two guage wire running to it so you all think that helps
I'm not entirely sure, but I think with your setup having a new battery and alternator you'll be fine for a while but you'll soon see your lights start dimming a little more every time you start your car and audio system. I was told that the dimming is gradual as you put a strain on your system.
A capacitor won't do anything, if you need more power, you need a new alternator. Unless you're jacking up the volume with the car off, then you'd definately need more batteries.