We have a 2017 X3 with the 16-speaker HK system. I think it's more than sufficient for car audio. BMW's user interface is still annoying to me, but that doesn't affect the sound, obviously. My wife uses it mostly for classic rock, and I tend to listen to classical music (both on Sirius), and it seems to work equally well for both.
Tire noise makes good bass very difficult to achieve in moving vehicles, especially those with big, wide tires. If you try to over-power the tire noise you generally get obnoxious, thumpy bass that sounds stupid at a red light. IMO, car audio is good only for the most casual listening.
We have the fancy-pants Bang & Olufsen audio system in our Audi S3, and IMO it's a waste of money. That was the one car I bought that a dealer ordered, rather than custom-ordered, so it has a useless nav system and an over-priced audio system. I generally recommend people don't order the fancy-pants audio systems; they're not worth it, unless the vehicle is very quiet, or you like listening in your garage.