see what is my plan...if i run the d5 line amps im gonna use the 400.4 to run the front components and have the HU (clarion dzxblahblah music catcher) run the rear quarter speakers. I could go all out and have 6.5's and 5.25's in the doors along with the kickpanels but that seems drastic. if i go with the d7 series they make the 6 or 8 channel amp i could use to push all the cabin speakers so that would work to. I for sure plan on upgrading to the optima yellow or red series battery. The reason i asked about the rear battery was to eliminate the frequency/distortion problem ive heard of have when running long power cables. What size/brand cap would work best? i was thinking stinger 1.5 or 2.0 farad?