I almost don't want to play. So many nice systems described so far and mine is not all that. However, my favorite system was 25 years ago in a 1992 Eagle Talon.
Panasonic VZ808 (a rare head unit)
PPI FRX-322 in dash crossover (mounted in console)
PPI A300.2 x2
MB Quart Components
JL Audio 10W1 x2
It was a very simple setup that was very clean. I wasted more than a gallon of gasoline sitting in the driveway listening to my CD's. The system actually started with two PPI Pro Mos 50's and was upgraded to the 300.2's. The two 10's eventually became just one 10". There many small changes but overall that was the best sounding system I ever had.