I have the same problem
I have a kenwood 1000watt amp and 3 mtx 10's <parallel box> by crutchfield.com. Whenever I turn it up at night the lights flicker on and off. I have a digital rockford-fosgate cap, and a high output alternator. I was just wondering why the lights flicker on and off so much? Also when the car is on, the current readout on the cap is between 13- 14 volts. If i added another battery would it balance out the load? and maybe make my lights not flicker? I use the monster cable 4 gauge set from battery to cap, and 8 gauge from cap to amp. I have another battery ready I could use.
Pioneer Premier Head Unit, 2 6x9 Alpine's, 2 3' Kenwood, 1 Kenwood 1000w amp 3 MTX 10's