look, amp makers put fuses on their gear to protect their products. therefore, an amp will have a conservative value fuse to protect the amp from blowing. so how much current does your amp draw? how many amps can the fuse hold before it blows?
done. that's your draw. that multiplied by your alt's output voltage is NOT your RMS. at best a car audio amp is 90% efficient.
NFrazier, stop posting. you're misleading people and giving people the opposite of what they're here for.