Originally Posted by kenchan

you will need to route the wires from the HU to the Polk's crossover, then the tweeter and woofer wires split. depending on where you place the crossover (either in the kickpanel or in the door) you will need to route a new wire through the door grommet which is a pita at times. they are drop-in replacement for the door (no spacer needed). you will need to modify the tweeter basket to make them fit which is really no big deal.

yep, most HU will have plenty of output to power these polks.

you and i are both music people so we both know that better speakers will generate better, natural sound vs processed sound. so ideally you want to swap out the speakers. but from convenience point of view, as long as you have a HU with good EQ and audio processing, the stock speakers can be manipulated to sound decent.

if you want to go loud you will want to lessen the burden on the door woofer and put more bass output from the future subwoofer. if you're planning to do a sub you should do this together with the speakers so it will be easier to find the crossover point between the sub, woofer (mid-range), and tweeter.

hope this get you started.