got a usa 230 head unit with 4 rca,s out front left and right ,, rear left and right with fader built in The amp is a Dominations Elite Series 4 channel , so the rca from the head unit plugs into 4 jacks on amp, how do I hook up just 2 rear speakers and 1 Sub. after we take care of that then to set it up gain,HPF,LPF all French to me