Factory dual batteries, tied together with at least #1 wire, or larger.
I figure some of my issue was possibly because I have a bunch of stuff (lights, fuel pump, radio, etc) tied into the one battery, which I switched sides to the one that has nothing on it. I also upped the supply to 4ga, which should make the issue worse, but it should also make the amp work better assuming it wasn't getting full juice.
The only thing I was thinking about, which I think Mac eluded to, would be to icrease the feed line between the alternator and batteries, but I'm not sure I feel like tracing that out in the harness...
And again, it is just a straight 4-pill.