I am out of the loop for knowledge on high end auto music systems

A Porsche forum would probably be your best bet. No doubt there are forums dedicated to the 944.

As a veteran mobile audio installer, I can tell you that you’ll definitely want a system that allows for EQ, preferably by way of DSP. I imagine some headunits have it built-in these days. You can get analog EQ solutions from the Audio Control company. I’m not sure what the top brands are these days. Years ago, they were Eclipse, Audison, Hertz, Memphis, Pioneer Elite, and Soundstream to name a few. 

I owned a near-mint 89’ cobalt blue 944S when stationed in Germany 16 years ago. Fun car but abysmal to drive in the snow. 

Check out Crutchfield.com. 

Thanks for your input, whatjd.

944/968 is so poorly noise insulated... why bother with a high dollar car hifi in that?

for great functionality, decent sound, throwback cool with modern touches... https://www.suncoastparts.com/product/SKUCLASSIC.html?gclid=CjwKCAjwwdWVBhA4EiwAjcYJEKelMWiINMg7ZBFnpJNAy_SkYOMzFEXGo8ylm6v6srlvkxfYZJVSWBoC0TIQAvD_BwE

first and foremost, driving that car is about windows down listening to the tires talk to you near the limit - remember, a chirping tire is a happy tire