From the states you can easily get 260amp alternators...
I'm building a audio car for my business at car shows, I'll be running 10 x 10" subs
7000w rms via 2 amps
4 x 8" mids in each door, run by 2 x 800w rms amps
To help power all this will be 5 batteries...
Just need hi output alternator to...