Take a look at some Kicker i57.2's.
They are 5x7 loudspeakers with outboard crossovers. Tweeters are titanium dome and can be mounted coaxially or freestyle (they can be rotated to aim at the listener). They cost me $158 from an online etailer. Don't waste any money on the back door speakers. You can barely hear them.
For the rears, I used a pair of ADS 320is'; 5 1/4 mids mounted in the rear deck and the tweeters mounted on either side of the back seat firing forward.
