If you don't listen LOUD all the time I'd just build a NICE SQ front stage and add something like I did for when the mood strikes. Only took a few minutes playing with the gain on the rear amp, so when playing VERY loud soundstage is still in front of me, but it sounds MUCH louder/fuller.
Personally not all that worried about perfect imaging, staging, etc... just like it to sound good to me and get very loud at times while still sounding good.
I've demoed my system for plenty of people, most with systems in their cars, and NONE have ever commented on the rear fill being a bad thing. They all just comment on how loud and clean sounding it is, even at VERY high volumes.
Or you could build a KILLER front stage as you mentioned as that will skin the cat also.....