Concerning high end audio names in new cars

I happened to have Mark Levinson in my previous 2 GS450h (2008 & 2013) and found them super good. ML produced clean and clear sounds especially the mid-bass. 99% of my friends when sitting in my car, they all said the sound system in my car sounded fantastic and they asked why:-). I just pointed my fingers to the "Mark Levinson" logo on the Head Unit to them:-). Even now, some of them occasionally asked me to give them a drive around just for listening to the music in my car:-). They told me their next car will be Lexus with ML in it. I never liked ML (not for its sounds but for its nasty lawsuit history of pushing Mr. Mark Levinson out of the group) but I have to admit that ML produces great sounds. I listened to Burmester in Mercedes E450 and GLS450 but still prefer ML in my GS450h. 

20 years ago I bought a new car with Bose, it was incredible. Better than anything I had heard before in any car. 

A maker is totally at the mercy of the varying, hugely challenging acoustics/materials in the myriad of car models

or they get a car, fully completed and they can tweak their system to sound the best

There is an Italian company by the name of Audison that offers "Sound Packs" for quite a few specific manufacturers and models. I have an all Audison sound pack in my '17 Golf GTI which includes a sub in the spare wheel well that does not require removal of the spare. I had sound deadening installed at the same time. It is good. Nowhere close to a good home system though. 

I have a "Fender tuned" system AKA Panasonic in my 2017 VW GLI and I think it sounds just fine. I wasn't expecting much after all I am listening in a car.