I bought the Memphis16-PRX5.550 and have a question it has a input selector switch that has 2,4,5. From what I get from the manual it put it on how many inputs you are running. I using the stock head unit and with line out adapters and have only for rca's to it so I would put it on four correct. If I had rca's plugged in on the sub channel it would need to be on 5 correct.