What do audiophiles do in their cars?

I have a 2018 911 and it came with a Bose upgrade but who cares. When you get above 30 you can only hear the engine and wind which is what I like. Porsche offers a $6000 Burmester upgrade but unless you just drive around town it makes no difference. Perhaps on the Panamera it might or the new all electric.

From the early 80's, I had a number of after market systems in all my cars.  My last serious project was in 2014.  I looked at many options at updating the stereo system in my BMW 7 series, but was limited with the depth in the doors.  So for the sake of good sound I decided to buy a Holden Caprice V8 (about same size of the 7 series) to add to my collection of cars.  I removed the door trims and added about 200kg of Dynamat panels to all the walls, floors, boot & engine compartment.  
Each front door trim was customized for 2 X 7" Focal K2 Kevlar Mid Bass Drivers, 7" Focal K2 Kevlar Midrange and  Raal 70-10D Ribbon Tweeter.
In the glove box I had a Clarion Head Unit (copper chassis) with separate DAC. 
I also placed to 2 X Focal Audium TD5 Tweeters in the dash running from a proprietary digital processor to improve staging.
In the boot I placed 4 X Soundstream Human Reign amplifiers, an Audio Control Electronic Crossover with Processor and 2 X 10" SEAS L26ROY subwoofers in 1ft cubic boxes for each. 
The SEAS 10" subwoofer is the best I have heard for speed and musicality for a home system. It is capable of matching well with my Analysis Audio Speakers.  The Wilson Benesch Taurus Infrasonic Generator is the best subwoofer I have used.

While driving Apple Music or Tidal via onboard system… I don’t expect any good sound from it.. mostly focusing on lyrics and meanings…however, I also keep my Dragonfly Cobalt with Sennheiser HD 650 in my car and when I have to wait, for example, for my kid at the practice I’m actually using this mobile setup for better sound. 

First thing I did to my 2015 911 GTS was to upgrade the sound. 
Kline headers and IPE cat back exhaust was like upgrading to TEKTON Speakers and $3k isolation platforms!!!!!  ;)

Better sound than anything on this forum.