Unless you spend ridiculous amounts of cash 4" are best left to 15khtz + (no bass).
I suggest, custom MDF rings or pods to mount six inch coaxials in the doors. Or else you could go splits and use the doors & the 4" spots, but this will lower the soundstage more than if you mount a tweeter near the a-pillar.
Rear treble is a waste of money in my opinion. Who goes to a concert and faces the back of the room? But you need bass, it reverberates through your car and gives more even dB, rather than source focused sound. That is why most setups chuck a couple of woofers in your boot.
Tell me your budget, and what you like to listen to - bass notes, vocals, guitar solo's etc...
Also, i think there is an audio section. U mite wana use it in future and keep the guru's happy