Well, its gonna be power from the batt, rca/turn on from the HU, and ground somewhere by the amp.

As far as wires to the speakers, you CAn run new sets of wires to each speaker from the amp , or just run a batch of wires from the amp to the head unit, and patch in to the current wiring.. factory wiring isnt that great, but for the wattage im thinking you'll be putting thru them I think it will be fine.