A sub in an SUV will always intrude on space. I don't bother with big bass anymore, I just buy speakers that do the job for my ears.
As for the front dash speakers, If they are 4ohm and you replace the deck, could you not just run new wire to the front speakers from the deck and connect the rest of the speakers using the wiring harness?
I don't think you understand, it isn't an issue of rewiring anything. The head unit (stock or aftermarket) has four outputs. RightFront, Left Front, RightRear, and LeftRear. The Pajero has 6 speakers, running 4 off the Front channel. In order to run the "extra" pair without adding wiring and an amp or a strange custom head unit, Mitsubishi used 8-ohm speakers in the front dash and doors. These speakers are wired in parallel in order to maintain a standard 4-ohm load on the head unit.
If you replace the 8ohm speakers in the dash and doors with 4ohm ones, the total load drops to 2ohms. (total resistance is an inverse sum in a parallel circuit.)
The result, according to Ohm's law, is that in order to maintain 12V at the new lower resistance, more current (and heat) is produced by your amplifier inside the head unit.
Your head unit might handle it, might not. The right way to do it is to either:
* cut out the extra pair.
* Find some aftermarket 8ohm speakers (home audio is usually 8ohm)
* Wire in a 4-channel amp
There might be other solutions, like just going to a component set with the mids in the doors and the tweeters in the dash location. Or re-wiring some high-end 2ohm speakers in series (which I understand might sound bad.)
Anyway, personally I'm going to my door speakers with standard 4-ohm ones and see how that goes. I just thought you should know the risks! Oh yeah, I've also read that 6 1/2" speakers fit the doors. I just bought a set of shallow-mount Infinities to replace my blown door speakers. Good luck. <img src="/forums/images/graemlins/kewl.gif" alt="" />