For whatever its worth:
I don't consider myself an audiophile, although I *am* a musician. Which probably means my brain fills in missing sounds for me! However, the Jensen JHD1630B "Heavy duty" head unit, in combination with a pair of the forum recommended 5-1/4" Kickers in the dash, and an older set of 6" Jensen marine speakers in the overhead has literally woken me up to a new world! I find myself taking the Jeep just so I can listen to this wonderful stereo - and I usually don't listen to a car stereo all that much!
Although I have a pretty new JVC in the Mercedes, I'm now thinking that the 36 year old stock speakers could stand a change-out...
Check out the DIYMA for sale section, you can get some good deals there if you are patient and savvy to weed out the bad sellers...and I think you are primed to do this.
https://www.diymobileaudio.com/forums/car-audio-classifieds.4/