you dont need more then 1 alternator , jsut run 1 large alt mechman makes an alt for any vehicle make or model so just get one that fits your vehicle , they make an alternator all the way up to 450 amp i beleive , my suggestion is to buy a xs power 3100 for under your hood , if you have room for more then 1 then fit as many as you can under the hood , those are 5000 ccas each , the 4 batterys you currently have would be great for a battery bank in the rear of the vehicle , run atleast 5 runs of pos and neg from the front batterys to the back battery bank , and like i said earlier if you purchase a high end charger that can be applied when your not using the stereo , this helps maintain your gear and batterys , and helps keep the stereo playing to highs top performance ,