Estimating at the very top of the range, you've got about 4kw at ~80% efficiency and 500w at ~60% efficiency. That's a combined draw of 5,833w. Divided by 14.4v that's about 400A of current, more if your voltage drops. Figure that the 0/1 is good for about 250A and the 4 is good for about 100-125A, for a total of 350-375A capability.
But that's assuming you're running full blast on all channels simultaneously. On music you're going to be well under those numbers. If the wire is fused appropriately the only thing you have to worry about is voltage drop, which may or may not be helped by having another run.