look for a good 8" mid like old school ADS 8s
or, if you are set on Focal, try for the 7" mids.
if you want 3 way active, find a midrange & tweeter which fit's in the kick panels and be happy.
you can have speakers (3way) a good distance apart from each other.. but I don't suggest having (3way) with the midrange behind you
I would skip the rear locations almost entirely.
rear speakers are not important but they can be useful as rear fill. tweeters are not needed in the rear.