Smart move. They'll sound great with that Alpine. Do yourself a favor and get a Dynamat door kit. This will make a HUGE difference in any door speakers. Doors generally make terrible enclosures and rattle a lot. Its easy to do, just take your time, that stuff is sticky. My guess is, if you do this, you won't need the 6x9's in the rear, if Im reading your desires correctly. That said, a trunk makes an EXCELLENT enclosure for speakers. New 6x9's in the rear can eliminate the need for subs for some folks.

Spy