I one my early designs was thinking to go with a 3 way front with a center channel speaker and just use the rear pillars as mid range fills. In the end I decided to work with OE 9 speaker locations. With the DSP's I knew I could tailor the sound to my liking without any problem.
If have to do it over again, I might really consider going to a 3 way front with custom dual 10 sub and 4 inch mid range fill still using HAT speakers. Technically, with sub(s) in place, it really a 4-way front with the proper crossover settings in mobile audio.
In any event, happy tunes with happy trails.
Best for now.
Laredo X, Trail Rated, QTii, Sele-Terrian, Quadra Lift, Off-Road Adventure Package ii, Nokian Rotiva AT, Tow, AFE CAI, DiabloSport inTune 1000-DCX, Custom Sound System ( HAT speakers, JLAudio , Pioneer , JBL MS-8 & RF 3.sixty.3 -- see the writeup link below for more details)