One of the big problems right now that is depressing that market is the integration of the audio electronics with the rest of the computing power and electronics of the car. Most of those systems are proprietary so the days of just swapping in a better head unit and set of speakers are over. The factory amplification may employ built-in DSP & equalization so that you have to compensate for that, as well. My BMW required an expensive "adapter" (nearly $1K) to go between the factory head unit and the aftermarket amplifier, which also had to have adjustable EQ built in to compensate for the difference between the response of the factory amp/speakers comob and the amp/speakers I had installed. My wife's Audi does not even have a head unit per se. The display is built in to the infotainment system,w the display functioning for GPS, audio, bluetooth/phone, etc with all of the controls on the steering wheel and on the center console.. You'd have to cut a hole in the dash somewhere to add a head unit and you know that ain't happening! FWIW, her factory unit sounds pretty darn good.
