My wife wanted bluetooth so decided to do a full upgrade, including the (4) door speakers (left the dash tweeters installed which run in parallel in the factory wiring). Went to Crutchfield for everything (they make it dirt simple for fitment, parts, cables, etc.)...they include instruction for systems that have speaker amps, like yours.
After install there was a lack of good bottom end so added a 400w Rockford amplified subwoofer. The sub would not fit under the front seat(s) so it got Velcro-mounted under the rear seat in the center space, all cables run under the center console and carpet. When we need the extra cargo space I move it to the footwell so the seats can lay flat since they pivot down a little. Major sound improvement.