crossover use and speaker placement

The LCR speakers are fantastic sounding systems, but there is no way you could duplicate them in a car.  Using the same drivers is not the same thing at all, as at least 50% of the sound character comes from the crossover and the D'Appolito alignment and the way the woofers function in that particular volume ported enclosure.  You could never duplicate them in a car; well, maybe you could actually build a set and mount them in a van. 

Back to your application: mount an Extremis in each front door and basically create a 3-way set with your Focal components.  Keep the 3 speakers as close together as you can.  Set up a subwoofer with LP at about 60Hz.  Bandpass the Extremis woofers between 60Hz and about 250Hz.  HP the Focal component set at 250Hz (use the supplied passive crossover with each set.)  This should give you quite a bit of low-end punch.  I'd use one Extremis in each front door operating off channels 3 and 4 of a 4-channel amp, with the Focal comps driven by channels 1 and 2.  Don't worry about adding anything to the back doors until you get the fronts set up correctly.

Now, as to the outstanding set of mids and tweeters you have, purchase a 0.75 cuft speaker enclosure set from Parts Express or Madisound, mount your other Extremis woofer, one of the 125's and one of the Usher tweeters in each enclosure.  Port the enclosure with a 2" flared port for 30Hz.  Build a good 3-way crossover at about 400Hz/5KHz and you'll have a really killer stereo set for your home.  Just make sure your amplifier or receiver can handle a 4-ohm load since you bought the 4-ohm woofers.  Rock and roll.