IMO the Rear 6x9's should only be used as rear fill. After all, you don't go to a concert and have your back
to the sound coming from the stage do you ? If the bass has no port through to the inside of a saloon car,
the pressure wave changes when a bass note hits in the boot, means the back of the 6x9's will take a real
hammering, unless of course they are in some kind of own enclosure (which they are not on the IS200).
The bass from the subs may be pushing the cone in the wrong direction to the way it is moving, ie out of phase
causing distortion/possible damage.
An easy way around this problem and keeping the 6x9's for rear fill, is to remove the ski hatch.
It unbolts very simply & comes out in one piece, and can be put back easily when it comes time to sell your car.
(CLICK HERE to see how to remove the rear seat - then the ski hatch just simply unbolts)
Armrest up or down seems fine after that, though of course be aware anything loose in your boot may find itelf
a portal to do damage under heavy braking. However if you fit you sub/subs so they fire through the ski hatch,
problem solved :D
With many people upgrading to DVD systems, the rear fill effect is very much worthwhile IMO. 60-80% of the sound
should still come from the front components, though this is variable to personal taste and also the source media.
Also it does keep rear passengers happier too, depending on how often they are in your car.