Sudden spazmatic electronics in car..alternator? Other possibilities?

Sudden spazmatic electronics in car..alternator? Other possibilities?

Suddenly a few days ago my 2002 Ford Focus started having electrical issues..while the cars running the lights have flickered, while driving my stereo head unit clicks off then back on, my subwoofer goes out randomly, the speakers go out on one side randomly back and forth, the fuel gauge has twitched back and forth at idle, and a sound from behind the gauges in the dashboard makes a clicking noise at idle.
It was a total sudden onset. I do have a high powered stereo that I expected would eventually wear out the alternator..

For a few minutes I used a voltmeter to check the battery before start, then after start with it still connected checked the power from the alternator. Went from 13 to 14.6v.. with the stereo up and all lights on it didn’t drop below 13.4v. I’m going to check again and for longer later. Just wondering what else I may check out or anybody with this experience could tell me about it.. thanks