A bigger battery or even an extra battery is a fix for a marginally underpowered electrical system.
I'm going to say that amplifier will pull in the ballpark of 200 amps conservatively.
If you want to learn an expensive lesson, run an amplifier like this on a stock electrical system.
Big three will help, but in the grand scheme of things its not going to make a huge difference considering how underpowered your electrical will be.
I'm aware this isn't the question you asked, but I'm hoping that I can save you some money.
I would personally set the gain via DMM to match a realistic output for your electrical.