4 battery on a malibu

I am used to doing the typical install but never gone to the point of adding other batteries. I have a customer that had a wall built for his 2009 Chevy Malibu. He is going to be running two Sundown SAZ200D amps and he wants to add 3 to 4 batteries to cover the power for the amps. My question is what all am I going to need to wire this system complete. I know from reading some post I need an isolater to seperate the battieries. I know i need to run the batteries in parrallel, I know I need fused distribution block plus ANL fuse before the amps for Pos wire, Neg distribution block to ground to chasis for neg wire.

Is there anything else I am missing???

All advice would be much appreciated!  

You need an isolator for all the batteries depending on your philosophy. Most want the isolator between the main and audio battery to isolate the main battery when the system is not charging, or when the audio drain exceeds the charging capability. [ For that, a relay controlled by the alternator's charge light circuit is fine - search for my posts on the "UIBI" - the Ultimate Intelligence Battery Isolator. Otherwise "Smart Battery Isolators" or an MW728 that control a suitable relay (ie, same size as the UIBI relay). ] But if a believer in NOT paralleling idle batteries (as I am), then each monoblock in the audio battery requires isolating when not in use. (If not isolated, 4 batteries have 4 times the chance of failing, and if one goes, they all go - unless isolated in time.) Those isolators can be controlled by the amp's remote - ie, UIBI relays controlled by the HU or amp being on (instead of +12V from the alternator charge light terminal).    As to the need for inter-battery fusing and how they are to be interconnected, I'll leave that to you. If adjacent and physically secure, then fusing is not required. Otherwise fusing is needed at EACH end of the interconnecting link near each battery. As to how to interconnect, that too is up to you. If you want to follow the matched battery and matched charge & discharge philosophy, then do as appropriate (eg ImprovingLifeOfParallelConnectedBatteryStrings (that's for 48V telecoms, but it briefly mentions the key issues) or ConnectingBatteriesInParallel). Keep in mind that adding fuses/protection and relays/isolators adds resistance, but that can be largely compensated by longer (-ve) cables rather than a -ve duplication of the +ve circuit (if that's a concern....).