Whoa, whoa....on the Stradivarius discussion, or indeed -- any discussion of any musical instrument -- it's important to distinguish between sound issues associated with production of the source sound, and those associated with the
reproduction of that sound after a process of recording and resurrection. My experience is in woodwind instruments, and there are many variables that effect the heard sound of the live performance: the instrument itself has many variables -- the maker, the temperature and the humidity are all critical, on the day; the musician -- specifically, his or her energy and mental focus. And then there is the performance space, many of which have not been acoustically designed for the instrument(s) being played, including voices.
I think that's a quite different set of issues, and shouldn't be used to confuse matters.
The second issue is hearing, and from experience I can tell you that your ears do "break in" to different music, sounds, and the listening space. I've had experience in groups where the first sense is that the sound is really bad, and then you play and play and replay, and to the self....it's sounding great. And then you have a concert, and you're told it didn't sound so good
The third issue is the listening space. I'm no expert here, but I've hear enough acoustic specialists describe how spaces should be changed to improve sound quality, and how you should carefully position both the source and the listening position. I think it's pretty obvious that cars are severely compromised in terms of both these issues, so one's expectations should never be too high, especially given other factors, such as engine, road and wind noise
The fourth issue is, of course, the reproduction process. This has become a total geek space, so I refuse to comment, except to observe that some processes enhance, and others detract, and that mixers and associated technicians often seem to be as hell-bent on leaving their mark on the reproduced sound as the original performers.
However, like most of us, I love to listen to music while driving. I didn't order the HK option, because I've been sucked in before by supposed high end optional sound systems in cars (ie, Bose systems in Audis). Initially, I was disappointed by the system in my M135i, but -- guess what -- it's getting better!
(no, it's not --- it's objectively probably the same, but my ears are getting used to it, as they do when you play in groups for a while. Our ears notice the "change" in sound much more readily than the sound itself, but our brains quickly adapt. That's my line on all this.)