I'm running two 1200w amps in my Ram1500 to power two 12s and a front stage. I was having power issues so I swapped out my stock battery for an xs power D6500 (biggest I could fit), upgraded the alt to a singer 270amp, upgraded all wiring to 0ga, and put in a big 3 kit. That being said, on full tilt every so often I'll lose my components as the battery can't keep up when it slams for a few minutes. I'm building a bigger box for the 12s I've got, so while I'm at it I'm going to have my builder make room for an additional battery in the cab (it's a quad cab, so not a huge amount of space back there). The installer told me he'll be putting an isolator in as well. Here's my question though. Do I need that second Battery to be able to handle the whole system (ie, a d2700 with enough amp hrs) or will any sized battery work to support where the D6500 can't keep up? Space is an issue, otherwise the choice would be easy for a 31 sized batt. I just want to make sure I don't put something in that won't be able to support or make a difference. Thanks for the help.