Assuming you are not going to do the work yourself, I would start by finding a good shop that has a lot of experience with your specific vehicle and can work on it without destroying it. Then see what they recommend for your car.
I am out of the loop for knowledge on high end auto music systems
At one time I had also invested money and time in good stereo systems for good cars, but have been out of that market for too long. I would consider doing an upgrade to the stereo in an older used car I have, which is a '91 Porsche 944S2.
Where do you feel I should start on my info finding journey? Mainly for FM reception and multi cd (perhaps SACD} playback.