Alternator possibly bad. thoughts?

so long story short, i didnt drive my car for about 2 months, and the battery was dead when i went to start it. no biggie, jumped it and went on my way. now though, if i dont drive the car every day, the battery dies when i go to start it up. since yesterday, it didnt even have a charge after 4 hours. i have an aftermarket alarm and stereo system, but they have been on the car for years, so i dont see how they could all of a sudden start a draw on the battery. im almost certain i need a new alternator, but i dont have access to a charging system tester to let me know for sure. btw the battery is a red top optima, about 2 years old.

ok, so my battery and charging system checked out ok. the battery was low at 419 amps, and said it should be charged. anyway, so theres some sort of parasitic draw. its gotta be the stereo system since i unplugged the alarm and the battery still went dead. so my question is are there any known problems with draining the battery?