My head unit is at the helm so I only need to use (2) short RCA cables for my LCs. (3) sets of 5v pre-outs on the head-unit.
Set A goes to the in-boats
Set B goes to a PAC LC-1 and then to the sub-amp
Set C goes to a PAC LC-1 and then to the tower amp
Doing it this way gets me independent control of the sub and tower. I've yet to run into a situation where you want the tower speakers on with the inboats off -- but I could easily run another LC-1 for that.
Former owner of a 1987 Supra Saltare. Current owner of a Malibu 23LSV.