Before you all tell him he needs to add wire, does anyone know for sure what size wire is already ran in that car? I know that some Chryslers already have decent 1/0 ran from front to rear. If the Cobalt already has 1/0 ran from the alt to battery, your Big 3 is already done. All you need to do is run your amps directly off the rear battery. If you need to upgrade your battery, simply replace it with a larger AGM battery. If you need more power than one battery can provide, simply parallel matching batteries in the rear with 1/0.