I have avoided scratching the speaker upgrade itch since N802. I guess I'm a Luddite. Maybe D4 will change my mind, but honestly, I usually see and hear more
tailoring of both sound and packaging than improvement. If I'm not mistaken, there are several world class facilities (Deutsche Grammophon for example) still using Matrix and N generation. Maybe they can't afford to upgrade?
https://emil-berliner-studios.com/en/studio-tour