more batteries or more alts

2 alternators will yield about 400 amps of continuous current to charge a battery or batteries. each battery will yield more availible current than both alternators combined. BUT not on a continuous basis. If you are looking for shorter term maximum blasts for SPL and the likes, I would go with more batteries. Will give you more availible current to the amplifiers when needed at those times. I say go with a few more batteries located as close to the amps as possible. Then down the road add on another alternator.

 

I would tend to go with the batteries still, but it really all depends if you can keep an eye on your voltage. If its a continuous night of making your ears bleed, at lower SPLs then perhaps the alternator. If its a few songs now and then to show you can break the local sound ordinances, then batteries