Weird Electrical Problem, so frustrating... Options

[tonytutino]

All of this started when i got my amp/sub put in last month on the 19th. (Its a 800w amp powering a JL 12inch W3) Well, a couple weeks ago i noticed my battery didn't want to seem to hold a charge and eventually it just quit. So i bought a Duralast Gold battery from Autozone on the 16th of December (having them test my alternator too which worked fine) and it worked great up until today. It just was dead when i tried to start it. Didn't leave any doors open, lights on, etc. so i took it back thinking it was just a bad battery, well they replaced it and tested my alternator again and everything checks out... As soon as i got the new battery i drove 15 minutes to work and that was it. i come out 8 hours later and its dead AGAIN!
I have no clue whats wrong... even if the alt. was bad, i don't see how driving just a few minutes on a battery would drain it... anyone know whats up?

[tonytutino]

well i took out the alternator this morning to have it tested in a better way at autozone. they said it passed but just for kicks i took it to advanced auto parts right down the road. there, the dude said it was completely dead. after having to separate answers i went to another autozone, passed there. and yet another advanced and it passed. so 3/4 say its good. and the other one is probably just cause it wasn't hooked up right.

but i took it to my mechanic and he said my amp killed my high-mileage alternator and says i just need to get a new one.
looks like its just that simple, woop!

but will my amp kill the stock 70amp alternator again? i considered getting an aftermarket higher amp one but i would prefer OEM