I’ve never paid to upgrade but have regretted not doing so a couple of times. Current Tiguan standard sound system not great, as Winston says. My last private car (BMW 5 Series) was the closest to perfection (as a car) than any that I’ve had, but I regretted not opting for Harmon/Kardon as the quality of the standard sound system was probably the only thing I could fault with the car.
Based on that experience I added Harmon/Kardon to the new X1 order (Motability) but BMW are unable to provide the system as an option at present on any cars, so the option was cancelled by them ?