Focal make good speakers, I have the 165's components up front and their 6x9's in the rear. The fronts were a straight swap.
The OEM rear speakers clip to the 1/4 panel card and not to the chassis, so it's worth up pinning your new speakers to the chassis. In other words not a straight swap!
Indeed there is no straight swap for the rear speakers as attaching ANY speaker to the flimsy panel card will result in rubbish sound. Most 6x9s will fit well at an angle to the metal inner panel with just a few small holes made for the screws.
