Ok, im a noob to figuring out how much ampage I would need for any given system. Usually go by what others tell me or calculators. What is the technical way of figuring out how much amps you would need out of the alternator then battery power for any system. thats the general question. Then, my bro is planning on running 6000 rms system and we are planning on running powermaster alt and batts. what size alt should we get and batts to place up front and how many in back. We will be running this system in a 86 cutlass and will be using sundown 3000ds and spl15s. thanks again

you basically want to get as large of an alternator as you can. If you think about the power your amplifiers put out and how much current they need to produce that power you'll understand.

6000 watts / 14 volts = 428 amps that it would pull with 100% efficiency. Factor in that your amp may only be 80% efficient and they'll pull 535. That's just for the amps, not to mention the at least 60 your car probably needs.

However, this isn't to say you need to find some way to fit 600 amps worth of alternator under your hood. You'll just have to deal with voltage drop if you don't have enough current. But you get the basic idea that the more, the merrier.

I would say you should get at least a 200 amp alt, but many vehicles have limitations based on size of alternator. So that's why I basically say get the largest one you can. The extra batteries will help keep the voltage from dropping below 12 once the alternator's juice is used up, and ideally you'd like to not go below 12 too far. One or two more batteries should do.