What do audiophiles do in their cars?

In my 2009 E350 sport sedan, I listen mostly to prerecorded jazz, old school soul/R&B, or soft rock on SD cards.  Sometimes I listen to CDs, or stream Qobuz or Tidal via my phone. Same goes for my 2003 CLK500 coupe.  

I replaced the CLK’s factory radio with a more modern one, but kept the Bose speaker system. So I use a USB stick instead of an SD card.  

The E350 factory Harmon Kardon system and CLK500 Bose system sound good to me.

2016 F-250 lariat stock upgraded system ... listened to SiriusXM for a couple years.  Got tired of it.  Local rock/hard rock radio station works fine now.  ‘16 Taurus... same.  2011 Hayabusa.  Ear plugs in for wind noise.  No music... it’s best to pay attention.

I do some of my best listening in my car and since I buy good ones they last me quite a while.
It is worth the cost, time and effort for me to put a great aftermarket system in.
Using a Pioneer DEX P99 6-channel preamp only head unit CD player DAC with DSP and time alignment (retail $1300)
JL Audio 900 watt 5-channel amp and 600 watt 2-channel amp.
Focal 3-way components front and real with active channels and crossovers, custom install and door work.
Custom built Scan Speak Discovery 12" sealed subwoofer.
Took several years to tune the DSP for time alignment, speaker crossover frequencies and slopes and frequency response curve.
Sound stage is pinpoint, dynamics, volume and transparency are spectacular. Overall neutral full range sound with lots of music appropriate impact and slam. Love it.
Not for everyone because it took a lot of technical skill for the installation and tuning.  

Stock Mercedes Benz Bose. 
Listen to FM NPR.  For me, Hawaii Public Radio.  HPR1 and HPR2. 
I installed a sd/memory card module in place of the cd deck.  I only use it in pockets around the island where there is no FM reception.
Sound system influenced car purchase?  No.

I don't feel my car audio will ever come close to my home systems. I'm not going try.  I will certainly not put music on while driving, relax, close my eyes, listen, concentrating deeply into said music as I do at home.  I try to drive with open eyes, attentive, concentrating operating my motor vehicle. Which  I consider a destructive killing machine.  Not my recliner that gets me to the grocery store and post office.

Hello,
I had a HK system in the Mercedes. That was very nice. I have a basic Ford now with the Sync 1 system. With Tidal Connect it sounds really good. No more commuting to work so I don’t need anything special. My wife’s Honda CRV touring has nine speakers. It sound really great with Tidal app. A good source really helps.