Hello, allow me to play mediator here for a moment and give an explanation somewhere between left and right field.For the unaware, our friend Josh is somewhat of a musical and audio boffin when it comes to staging and acoustics, tuning, and well anything you can get sound out of. However, this expertise is thus far in environments lacking 4 wheels and a motor which as even he admitted, is a far different beast. Like comparing chalk to cheese if you will.
Now, regarding acoustics and staging in a vehicle:
Fritz you are indeed correct in that show cars quite often have rear speakers in them. This is because the rear seat is so far away from the front speakers that if there were no rear speakers (technical term "rear fill") then all the back seat passengers would hear is "DOOF DOOF DOOF" when they should be hearing "DOOF bitch DOOF ho DOOF n*gga DOOF bling"
The big thing to acknowledge is that a MightyBoy is vastly different from almost any other vehicle gracing this planet. (like you didn't know)
So in saying that, the audio setup needs to compliment the unique characteristics of the cabin.
In my experience, having speakers in door pods does not work effectively. Why? Because the cabin is so narrow your legs and those of your passengers will mask the sound. By the same token, placing speakers low behind the seats gives a similar result, with the seats replicating the effect of the legs I mentioned previously.
So what is the answer?
While I do not profess to have an ultimate answer for the masses, I can offer a couple of solutions that should be a vast improvement over those tabled.
Firstly, mounting a set of 6x9's high behind the seats in boxes would give good clarity and ample volume. When I had speakers mounted in this fashion they worked in exactly this manner. In lieu of the massive sub/speaker box I had you could mount individual speaker boxes from the rear wall of the cabin housing 6" or 6x9' speakers and still retain the majority of space behind the seats.
The other alternative is something that I will soon do and give results for: Mounting splits in door pods, but mount the driver in the pod and the tweeter on the dashboard... As I mentioned earlier, the drawback of having speakers in door pods is that legs will interfere with the sound. Being that only higher frequencies are directional, I believe that mounting the tweeters higher will give an uninterupted path for the treble to travel towards my noggin. The 6" driver being muffled will then become more of a minor inconvenience than a major headache.
But thats my $12.50 worth. (It started at 20c, but these things happen.)
However this does not have any effect on the basic principles of speaker design, or the ideal staging of a stereo pair. It just makes the task a little more difficult. 
It was adjusted to suit the predominant amount of hip hop that I listen too in the car, I can assure you that on the odd occasion that I listen to anything remotely rock/metal based that it gets a nudge in the right direction. 