What do audiophiles do in their cars?

All of you forum members with your killer home systems…what do you listen to in your cars?  Do y’all have custom stereo systems?  Does the quality of the stereo system actually impact your car buying decision?  I have a B&O setup in my 2021 truck, which was an upgrade and sounds decent enough, but nothing compared to a typical HiFi home system.
Generally, I listen to the sound of the V8 engine while driving twisty mountain roads. But seriously, a car is a poor place to put a high dollar system unless you are sitting still with the engine turned off.. Too much noise and too many cars on the road which demand attention.. So listening in the car is a casual thing. My listening chair at home has no such demands.  Cars now have decent systems. Wife's Avalon has a pretty good sounding JBL system. The older cars didn't have very good ones so I always changed out the stereo. Many people did the same. 

a sports car should have its own soundtrack - i have gone so far as removing all stereo head units, amps and speakers from my air cooled porsches to reduce weight (as well as some sound deadening), i never turn it on anyways

a cruiser/grand tourer should be quiet enough to have a decent stereo - meaning it doesn’t make playing driving music sound harsh, tinny or otherwise offensive - you can’t hold a car stereo to any standard similar to a proper home system - the key is the car being quiet enough so the sound system runs at moderate volumes and isn’t blaring and making harsh noises
I listen to sirius xm, which has poor sound quality. My oem stereo is not good and neither is the road noise. The setbacks of upgrading the stereo like removing panels is not worth it to me. The other problem is integrating a better stereo with the stock "infotainment" systems. In the heyday of car audio there were only like three options for a really good head unit. I would be surprised if that kind of sound is available today, but I do not know for sure. 
Who cares?
Yes the stock stereo sound and features have some bearing on the purchase. Both of my cars sound good enough with the top line trim.
I had a ’95 Ford that benefitted immensely from changing out the door speakers. Those days are long gone.
In a moving vehicle you will get far more SQ improvement from
sound deadener
instead of better playback equip.
If you wanna blow dough go Crutchfield.
I listen to inde radio for musical discovery. In Austin, I'm luckier than most for this option with 3 great stations, one totally local music. 

Keep the roof open, and let the warmth of the sun reduce fatigue from tinny treble. Cheers,

What ever the car came with. Putting any money into a car sound system is a waste of cash. 
1-sports-radio, local or Sirius XM.
2-Sirius XM music---channels on my preset = Beatles, Classic Vinyl, Classic Rewind, the Bridge, Blend, Tom Petty, Sinatra (classical and jazz don’t work well in cars to my ears).
3-never news.

my 25-30 minutes drive to work and home is my time to get my brain good, and not looking for stress-points. when i get to work or home i’m ready for it. in car with my wife it’s her call.....XM Fox News, The Bridge or Sinatra mostly.

i’m in the car business and drive demo Honda products with stock systems. these days they are quite good. never really warmed up to throwing money at in-car systems but can respect those who do. when i had my 2016 Porsche CS2 for 2 years i listened to the motor mostly; it did have Sirius XM so listened to that too.

nothing is going to compete on any level with my home system anyway......so i don’t even think about it.

and then there is my professional experience......

when we repair cars, appraise cars and recondition trade-ins we see lots of butchering of car’s systems by aftermarket and DIY’rs. it’s a mess. the sanctity of your wire harness is quite important. and the cost of pieces to replace is daunting. these bad installs can actually total a car in some cases. so i’m not a fan.

the ultra serious in-car stereo crowd is a whole separate culture and that is another subject entirely. i do understand that passion and don’t mean to disrespect that.
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When I'm alone I listen to myself yell and cuss.

When I am driving my wife I listen to her yell and cuss.

We live in the Los Angeles area.

I leave my audiophile brain home and just listen mindlessly like I’m listening to Alexa.  We all preach how important the room is in getting good sound — the car’s interior is an audio nightmare, and to make matters even worse we sit on one side of it.  Game over IMO.  I focus mainly on driving anyway and wish more people did the same.  
My Toyota Tundra has the upgraded JBL stereo.  I use it to listen to books on CD.  Recorded music listening is strictly an at home activity.
Couple times a year love to take out highly modified (just as my home stereo equipment) 2011 Mustang GT vert, top down listening to streams through Ifi IDSD signature and highly modded car system. This in no way approaches home listening, noise floor with top down ridiculously high, this for kicking it out with music I rarely listen to at home. Forget about dynamic range, all loud works in this environment.

When I’m alone I listen to myself yell and cuss.
When I am driving my wife I listen to her yell and cuss.
We live in the Los Angeles area.

i use to have a 45-50 minute commute, with about an extra 10-15 minutes a day from congestion.

since COVID i have zero traffic congestion during my 30 minute commute. i get on the freeway in 5-6 minutes from my home, and set the cruise for 75mph and get off 20 minutes later at the exit near work. reverse back home. the silver lining to all this chaos. unfortunately in the car biz when people are not driving they don’t need you.

in the Seattle area all the techies and academics are not going to work; Amazon and Microsoft (and the majority of other tech) are still closed working from home. they mostly all live east of Seattle and commute to the west. so east<->west freeways are empty. blue collar are back to work, they commute north and south, and those freeways are worse than ever now.

the new normal.
Years ago, I had the Honda/Bose system and later the Mark Levinson system in a Lexus. I don’t recall the sound being anything special. These days, Honda and others probably, don’t even offer a CD player. For my money, I believe the best spend is for Sirius/XM radio. Favorite channels: Beatles; 60's; 70's; the Bridge. 
I have a Ford E350 with AM/FM , 5"  full range door speaker....   my Vette is rocking the Delco / Bose....   doesn't get any worse, does it?   Makes me appreciate my home system after driving 5 hours a day in my van.   I actually have a Altec Lansing  Blutooth speaker in the van , also crappy but I can stream...

I think car stereos have actually evolved to where most people are content with them, thats if you get the premium sound / entertainment package
Depends upon my mood or how long I'll be driving - Sirius XM, cds or IPOD - doesn't matter if I'm in my Porsche, Caddy or GMC SUV - need music
i thought the X-50 option was the sound system, silly me….

for a while my LA commute was a helo from Seal Beach to Canoga park. I can highly recommend that….
By myself I enjoy peace and quiet. Don't listen to music hardly at all then in the cars or van
Memphis audio makes very good reasonable priced stuff. High end Focal or Dynaudio. 
But yeah my take it don’t spend a fortune on a car stereo. Also horrible ROI when you sell it. 
I listen to the roar of the 500 HP V6 in my Alfa Romeo Giulia Quadrifoglio.

When I am with clients I tone it down and let the factory HK Sound System create some background noise to sooth my customers nerves. I can scare some folks with my driving LOL.
I like mine after 100 sf of deadening stickum', a million watts of little Class D amps, a 200 watt alternator, a cap pack, isolator, 1 10" sub and swap the stock speakers out for comp speakers. The wife just loves it, so do I.
Factory head set with CD and Cassette (rare) special order, all leather too. 

We drive to pick up my grandson 3 times a week at his 1st grade class.
35 mph on good roads.. Its pretty good actually. As good as a BMW as far as road noise maybe a little quieter. It's extremely quiet for a car, NOW. Toyota Camry.

I have a EB F150 with an Alpine/JBL comp system in it.. 
LOL it's fine, parked with the bed tipped and the doors open.. A little Carlos. :-)

Everything was done by me, I'm picky.. Mead's set up tools are really nice to tune in everything correctly..

Throw me in with most everybody else here in this thread. I'm fine with my Subie's standard issue audio. I'm just not concerned with the stereo in the little two seater sports car.
The furthest dip I will take from my main system is my headphone office system. Once interested in a car system, I now will not listen to music in the car. On Serius/XM in the car I listen to cable news.
These days there is so much inter connectivity with the whole “smart” system that runs through the stereo seems it’s not like it used to be where you could just rip out the head unit and put an aftermarket in without losing a lot of functionality. 
The Bose system in our Escalade actually sounds pretty damn descent. Especially on 5.1 dvds. 
I listen to a 64GB usb stick with low rez copies of my cd collection, and FM.

Good enough on my premium stock Subaru Outback system.
Silence is golden now as I mostly just enjoy the drive, even on marathon road trips which are common in my Malone tuned 2015 VW TDI SEL.

Its system is NoFi HiFi. If I listen in the car at all it’s very brief amounts of Radio Paradise via iPhone Bluetooth - my car’s sonic preference, go figure! A Volkswagen / Panasonic badged “Fender” system. Use of the sunroof shade door as a treble control with everything set works wonders - just open for exposed glass surface if more brilliance is required.
It was a different story though 40 years ago when cassettes ruled.

For all you old-timers it was Concord head units with matched azimuth & speed to my home Nakamichi 480 before graduating to a Nak CR5/TD700 combo that was my game over source. Typically paired with ADS power & main spkrs 👍
I used to spend money on upgrading the stereo system.  After market when I was younger then buying the premium audio.

I stopped doing that as my home system go better because it just couldn't hold a candle to it.  I've had factory Burmister's, Harman Karmon, B&O but the last 3 cars I didn't make decisions based on the audio. 

Unless of course you counting then engine.  Then that was the first criteria and option.
I have an Acura 2009 which came with a Elliot Schiener/Panasonic 5.1 DVD Audio player.  When I got the car in 2009, DVD-Audio's were already out of print. However, I was able to buy around 30 oop DVD-Audio discs from Ebay, Amazon and other music sites - as well as burn a ton of 5.1 discs. 

The better discs like Hotel California, Rumors were recorded at194 khz/24 bit even back then. To this day, I feel that the sound in my Acura is better than the analog sound from the system I have at home, which is not too shabby. For the first few years, I was really into my car stereo and the 5.1 sound. But like everything else, it got old. I'm more into 2-channel now, but I still have all my 5.1 discs (< 100) and will occasionally listen to it in the car, especially during longer trips.

XM radio on that sweet, sweet Hyundai stereo system. Occasionally I turn that off and listen to the rattle somewhere in the passenger seat frame.
I have always believed that what one "does in one's car", however disgusting, perverse, illegal, or jaw-dropping weird, is one's own damn business.
If you want to hear the good sound in your car , first it neeed to be luxury like Lexus LS sedan or mecerdez s class they are well insulated from inside dead quet and you can enjoy mark levinson in Lexus or high quality brand audio in mecerdez Benz , that what they designed for !
What do audiophiles do in their cars?

While I'm driving or parked?

If it's when I'm parked, I'm not saying!
XM Radio with whatever the best "optional radio with *** speakers is available. I think the Pacifica has Harmon Kardon 20 speakers and a sub, and my Corvettes always had a Bose system. And I must have the "optional biggest wheels and tires on whatever I buy. My wife has grown to accept that I will absolutely not buy a car without a Sunroof, great radio and nice wheels and tire package.. Always runs the price up on my automobiles, but why make payments on something I don’t want ..
The 14 speaker “Lexicon” in my Hyundai Genesis is remarkable to my ears, depending on the source, of course.
Have an Infiniti with one of those run-of-the-mill Bose systems with cardboard speakers and a horrible sub. Kept the stock head unit, speakers upgraded where easily accessible (to match the amp had to find 2ohm high sensitivity speakers). Replaced spare-tire sub with better spare-tire sub. Dynamatted all the doors and floors. Maybe $1,000 and some of my time for the work? Marked improvement, but as others have said, hardly a controlled listening environment. 
I use to listen to my wife but Dekay’s wife’s complaining is more interesting-as always, stuck in LA traffic
I use the stock system in my VW GLI and stream Qobuz or the Relisten app from my phone.
CD's in a fair system for 2008. Fosgate? Except the subwoofer under the driver seat. Useless except for gluteus massage. I turn the bass control down to zero. Sometimes I run a Patch cord direct to my V40 phone for Tidal. It has an above average Dac.
Stream Tidal over my android phone on my 2020 Lexus ES350 UL with the factory Mark Levinson stereo. Sounds pretty good for a factory stereo but the car is very quiet.
Pulled the stock Ford stereo out of the truck, put in a Sony WX900 & a pair of Rockford Fosgates. Stream Qobuz high rez. Sounds very nice.