Adding Second Battery

Im going to be running a roughly 1300 watt system (maybe maybe sometimes 1500 but rarely very rarely at that) in my 04 jeep liberty v6. I have big 3 in knu 0 guage and stock battery (which is very small and saw slight dimming off 500 wrms without big 3).

Im aware i could get a HO alt but im not nearly in the financial situation to do that. So my next best option is a second battery, or replacing the current one.

So should I add a second battery or get a big nice one under the hood?

I was looking at what XS has to offer and thought the D680 would be good to power the sub amp and leave the stock battery for the mid and high amp.

The amps are:

mb quart onx1.1000d (subs)
mb quart onx4.60 (mid/high)

I will be running two sundown e 10s d4s at one ohm and then the 4 speakers at 60rms ea off the 4.60.

So what should i do?

and could someone point me in the correct direction of a thread or video on how to properly hook up a second battery so i can research and learn.

thanks.

Get a Sears Die Hard Platinum Deep Cycle AGM battery to replace the regular "Cranking Battery" you currently use under the hood and you will be golden, or the biggest XS, Kinetiks,etc. that will fit under the hood. It is not very smart to mix battery types in a multiple battery system anyways. Ideally, you need the exact same battery(ies) in the rear as you have under the hood to get the most battery life and ensure proper sync during charging/discharging cycles.

THANK YOU SO MUCH. haha thats going to help a lot the whole not mixing batteries thing