Do you care about car audio?

I recently replaced my stock car stereo and had an ARC Audio 6 channel amp/ 6 speaker active crossover/Sony head unit and a 10" sub placed in the passenger footwell. Best money I've ever spent.

It is MUCH more enjoyable than stock....Do it.

Best receiver I had was a alpine bought in mid 90’s after the clarion bit the dust.  Had the tape deck for al,ost 20 years

Used to care more back in the days with separate drivers, amp, cassette deck. 
After that all the cars i drove were leased ones so no room for experimentation.
Today my Giulletta has a decent factory installed unit with connectivity and that's fine for me.

Noticed someone else mention Soundstream... In the mid 80's I had two Soundstream class A50's running MB-Quart coaxial front and back with a D100 powering the sub - also Soundstream cassette head unit with the adjustable azimuth control (same a the famous Nacamichi "Dragon" head unit). All KimberKable (isn't that crazy!). That system was awesome - for a late teen/early 20's guy in the Army.
Later, I replaced those 'fry-an-egg' class A's (honestly, if you touched them you'd loose skin) with high-current (labeled "cheater amps" because they double power down to 2ohms) Phoenix Gold MS/MQ-series. I've run those since early 90's and still do. Yes, they've been moved through several cars and trucks over the years. The most recent incarnation is setup like this:
- High-end Kenwood head unit to an active 4-way crossover
- Phoenix Gold MQ-430 (4-ch) running tweeters and mids in the front doors
- Phoenix Gold MS-275 (2-ch) running the 8-3/4" mid-bass also in the front doors
- Speakers are Morel 3-way separates (1990's version of the Elate TI-903)
- Orion HCCA-275G4 (another old-school "cheater" amp, last of the US-made Orion HCCAs and doubles power down to 0.5 ohms) driving a
- Stereo pair of 12" Image Dynamics in a custom sealed enclosure DIY'd to fit behind the rear seats of crew-cab truck.
- Massive amount of sound-deadening material throughout.

Audio-supremist can talk bad about car audio all they want, this system sounds amazing (even compared to various incarnations of my 2-ch home systems) and has given me such enjoyment for so many years. Morel drivers (at least the ones I've used) are something special.

It was actually the sound from this car audio system that lead me to open-baffle, when one day I realized how much better the sound was with the windows down (and air pressure was free to escape the inside of the door cavity). Now everything else in the 2-ch home system sounds like listening to speakers to me - like flipping a switch from live (open-baffle) to recorded (box speakers). The other aspect it taught me was the benefit of active crossovers for amp effectiveness and overabundant power for current stability and driver control. 

All these years and I still marvel at the sound quality.

I've been into both home and car stereo for a very long time. I'm a bit surprised how many don't seem to care much about car stereo. Maybe that is because I do more long drives than your average Joe. I have probably listened to more music in my car than anywhere else.

When I buy a car I always look for the most basic stereo option. Then aftermarket upgrades are simpler. Many of the modern OEM upgrades are tougher to remove and IMO nearly every one sounds pretty poor. They use poor components, underpowered amps, and too many drivers. I've heard various Harmon Kardon and a few Mark Levinson OEM upgrades and while the latter ones were decent not nearly as good what a couple grand spent in an aftermarket system can provide. 

For maybe $1,500 one can easily upgrade the amp and front speakers to get a huge improvement. I usually spend a tad more to do a bit of sound deadening, high quality 2 or 3 ways drivers, and a sub when I am feeling rich. Given how much music I listen to when driving it is a great use of $$ for me. Imaging is always tough of course (mainly due to available front tweeter positioning) and the fidelity in a car is very different (and not nearly as good) as what one can get at home.