I've had a multitude of different configurations in my MJs and the best was a 4way amp feeding 5 1/4" components in the doors and a high quality 10" sub behind the seat. I used to have 4x6s and then 6x9s in the rear corners, but once I added a subwoofer to the mix, the rear corner speakers were essentially worthless. higher frequencies were always muffled by the seat, low frequencies sucked and were drowned out by the sub. So I eliminated the sub's amp and the rear corner speakers and the sound was incredible with minimal space-eating parts. :D
here you can see the tweeter location: