Component speaker question
 

I've got a P-5 I would like to put in the MB quarts premium series components in. 5 1/4" mid in the front doors and tweet in the sail panel. Now the question is about the rear doors, should I put in an additional component set 6 1/2? or 5 1/4? with the tweet low in the door aimed for the rear passengers? Or should I just get a set of coaxils for the rear doors? Or make a sealed box for them and integrating them into a sub woofer enclosure in the trunk?
:----====----:----=======----:----====----:
: mid : sub : mid :
:---------------: :---------------:
: :
: :
:-----------------------------------------------------:

I want to be able to drive with the windows down and have the passengers in back still be able to hear the music.