just because your lights dim, does not mean you have to have a new altenator. My lights dimmed with my PPI A600 (uses 1 40A fuse) when used it for bass. My lights dimmed more with lanzar vibe 1200. They dim even more with the M3000D 4x40A fuses. I still get by. I play loud for long time, but I cannot tolerate max loud very long, so battery lives. Do not waste $ on a cap. Do not expect high current with lights, air/heater fan maxed.
Also upgrade you ground wires, I added a 8ga to the bracket over the alternator, and a 1 gauge from the batt to the shock tower, and scraped off paint to get good connection.
I put amp under pass seat, to shorten power wire length.