Well apparently it does take some intution. Because most people seem to think that if you have a 2500 watt mono block, that you need to have multiple runs of 1/0 when running a stock alternator (keep in mind this is for noncompetitive situation). As in my first post the current flow from the front of the vehicle to the rear battery bank cannot exceed the amount of current produced by the altnernator and battery. It doesn't matter if the amplifiers are drawing 500a, the rest must be supplied by the battery bank. Which means if you just throw the 500a of amplifier draw into the simple calculators, you are going to get some extremely inflated number with regards to your power wire needs.