Edit: to answer your question below, I like both, active and passive listening. But I wouldn't try to optimize for active criteria like details in a passive evironment like a car, so I'd spend more money on fun things like buttkickers instead of high end detail.
Also soundstage can be greatly improved by placing speakers on non factory locations because manufacturers usually prioritize packaging above all else. A tweeter placed at the bottom of the A-pillar near the windshield is the worst possible location and sounds like it was put in a tin can.
Background noise in a car also has a solution, turning up the volume. Plus getting quiet tires.
Music lovers buy stereo systems to listen to their music.
Audiophiles buy music to listen to their stereo systems.
There's a reason mix engineers have always done 'check the mix in a car'. It might be way more revealing of what's happening in the bass, even when the speakers are relatively weak. Once you get anything decent, watch out. It's a bit like having your whole body inside headphones.
Ripping the car apart to install sound insulation might void your warranty.
I have a Bose sound system in my car with 11 or 13 speakers (they're everywhere), but the car is so poorly insulated that I have to turn up the volume quite a lot at highway speeds, or even after about ~ 35-40MPH.
On my Toyota it only involved basic removal of interior panels, I can't imagine that affecting warranty or resale
There is a reason premium audio car packages cost over 2000$
And I used to own a Jaguar XJ that (while the car itself I had to get rid of after the entire cooling system shit the bed for the second time) was the quietest car I've ever owned and not even close, despite being a 5L V8. (The Jaguar also had probably the best sound system I've heard in a vehicle - 1200W B&W 7.1 channel, 20 transducers).
I am looking to purchase a new car and through test driving it has a better sound system on paper with more speakers and a subwoofer and the sound is limited by the performance of the Bluetooth connection.