KungFuPimp

I'm at my wits end trying to figure this problem. I don't know it's my amp, battery, or alternator. I have one Kicker sub amp and one Alpine 4 channel amp. The problem lies with the 4 channel amp, it keeps turning on and off. It only happens randomly. I have checked all connections and they are tight. I checked all fuses and they are good. I also have relocated the ground for the 4 channel amp but the problem still continues. The gains are not maxed at all on both amps. I have checked the voltages multiple times and there are the results : All measurements are at car idle. Both amps on : 13.79 volts - 13.81 volts Both amps on and AC running : 13.79 volts Both amps on, AC running, and rear window defroster on : 13.69 volts Both amps on, AC running, rear window defroster on, and wipers running : 13.69 volts Both amps on, AC running, rear window defroster on, wipers running, and headlights on : 12.32 volts There's another wrinkle in my problem. When the 4 channel amp is turning on & off, the voltage at the battery and at the 4 channel amp would fluctuate between 11.50 volts and 12.75 volts. The sub amp is always on regardless of the 4 channel amp problem. When the 4 channel amp finally turn on, stay on, and have sound output, the battery voltage would stay at a constant 14.17 volts. Is this a sign of my battery about to die ? Or signs of an alternator about to die ? Faulty voltage regulator ? 4 channel amp about to die ? I have gone to numerous Auto Zone and O'Reilly's to have my electrical system checked out and all of them said that my charging system is okay. But I would like to have your input. If it's the alternator, is it advisable to get a high output alternator ? And if I do get a high output alternator, do I need to up the fusible link amp rating ? BTW, these two amps are installed on my 300ZX with a factory 80 amp alternator. Any help would be greatly appreciated....Thanks !