hi i need some help with my system. ive got 2 sundown 10's an a 1400 watt hifonics amp. even though my truck has a decent electrical system as it is stock, the voltage still drops sn i want to put another battery in it(it has an extra tray for one). when doing this, how would i wire them up an do i have to have 2 of the same batterys or can they be different. really dont want (or have the $) to buy 2 new batterys. any input appreciated