My thought process was that, while running, the alternator would be fueling the amps/aux battery first and also charging both batteries. Isolator I would be using is:
http://www.amazon.com/gp/aw/d/B0031...ywords=NOCO+IGD200HP+200+Amp+Battery+Isolator
That would keep my amps from pulling from the vehicle battery at all but still enable charging of both batteries.
I have a mean green 180 amp alternator. I have replaced all of my power and ground wires going from the alternator to the vehicle battery I currently have, as well as added grounds/upgraded the factory grounds and power wires with 0G wire, and 0G wire all the way to the amps, and I can still easily make my lights dim when the bass hits. I tried capacitors, even though I know those are only a bandaid to a problem. I know Nissan doesn't use the highest quality wires/connections. In fact, it's damn shoddy IMO.
Oh, I also currently have an optima D31M shoehorned into the X... I have a total of 23 speakers, amps running at 2ohms. Yeah, it's a bit much and I should probably cut back some of it but it is what it is.