I don’t have much experience in high-end luxury cars but I have owned a spectrum of brands from European,domestic and Japanese manufacturers.
Honestly I have never been impressed by a factory system. The H/K in our older Mercedes was a joke. We all know Bose is a gimmick. I’ve heard the Fender systems are pretty good but I’ve never had the chance to demo them.
The best I think I’ve heard is the Logic 7 in BMW.
What are some of your favorites?
The funniest bit is that those bespoke systems have one manufacturer, but are just premium branded, just badge engineering.
An excellent example that I’m aware of is PSA (Peugeot and Citroen) where the Hi-Fi option was cobbled together from different parts, like head unit from Magneti Marelli, Bosch or Harman, amplifier from a number of different manufacturers and speakers usually from JBL, all branded as a single Philips (in Germany and sometimes the Netherlands), Denon (in Germany and some other markets) or JBL (default in most markets).
So if you don’t like our don’t appreciate one brand’s credentials as sufficiently Hi-Fi, just get your car in a different market.