what amp are you running? at the minimum, i need to know if it is 1600w continuous or 1600w max. some amps have higher current draws than other even if theyre the same rated wattage. old school orions for example suck a ****load of current out. definatly upgrade your BIG3 to 0awg wire. thats always the first thing to do.

oh and xtra bats are for the most part useless. all it will do is add more strain to your alterntor. theyre just used often in competitions where the car isnt being driven.