As stated above, its rms you really need to look at. Now its been 15yrs since my last science class but if I remember correctly, its like this: watts/volts=amps. Amps are what you need to be concerned with. If you're killing ANY battery, your alt simply isn't up to par for your needs, I don't care what anyone tells you. Its a fact. A cap isn't ALWAYS a bandaid. You can only push/upgrade an alt so far before it needs help (this is where a cap comes in). Do 90% of people need a cap? Hell no. Now, for ANYONE to give you the info you're looking for, we need more info on your amp. For example, my old Kenwood was a 9152D (d signifying class d) mono block. And its sounding to me as though some were gently down playing KW amps on their RMS power. Again, is it a mono block? The 9152D is 1800pk and 900rms at 1ohm. That's NOTHING to downplay. You said you changed your batt? Ok. If we don't get some specs from you, your alt is likely next. Did your new batt fix your problem you think? No. It didn't. Your audio system is simply using up your batts reserve amps. Understanding any of this?