Battery Upgrade (gmc sierra classic 2007 5.3l)

Im am looking to power 5500 watts rms, I found a auxiliary battery tray for my truck for the engine compartment i will install. I would like to have to battery close to the amp but space is a very big issue for me. The only batteries i could possibly get in the back are the small 600 amp kinetik ones.

Would it be an issue to have the two big batteries under the hood, with there own runs of wire to two small batteries right before the amps? Will the small batteries help at all or should i just scrap the idea?

Also need to upgrade my alternator to something a little more powerful, Any recommendations