i have my amp wired to the back of the rear seats. from the amp, i ran my power and ground wire to my cross over under the seat. from the seat, i have four wires to the front door, did some custom drilling.
then 2 wires from the cross over to the rear speaker. (3- way)
now the hard part was getting the wires into the door. i did some holes through the body behind the dash. my power wire runs under the carpet, through the floors panel when you step in, under the seats, and back to the amp.