As you said, when your at an auditorium or concert hall, the music "sounds" like it's coming from all around you. However, it isn't. That's exactly what I try to replicate (and have done a pretty good job of) in the car. Granted a car isn't a sound stage friendly environment like the aforementioned venues. However, with plenty of time and tweaking, it can be achieved. I will agree with you though, it does take a bit of tricking the ears. You're just trying to replicate the immersion of the front stage at a venue, bringing that into an automotive realm.
I do agree with what you said, but in all reality it's the same thing, just accomplished in different ways. At venues they use acoustically tuned spaces. In a car, you use electronic adjustments. 2 different approaches, same end goal.
I do understand that some people enjoy rear fill, and you know what, to each his own. If you don't have the benefit of some form of digital signal processing, rear fill can benefit your audio setup.
Just as a note, it doesn't have to cost a lot of money. It's more time then money. The tuning and tweaking is what takes the most amount of time, and plenty of patience. I'm sure you know this. In total my system was under 800 (includes the PC, LCD, amps, comps, subs, wiring, everything). I'm EXTREMELY pleased with how it sounds and get comments about my audio costing more than my car all the time. I just smile and laugh, cuz I know the truth.
1.8GHz Northwood, Intel 845 Mobo, 512MB DDR, 1x20GB + 1x160GB, Intel GPU, SB Live 5.1
Phoenix Gold RSD 65cs 6.5" Drivers, Infinity Tweets, Pioneer 305DVC 12", PPI Sedona 630IX, Alpine MRP-M500