I stayed with Technics from he Kn1000 to the Kn7000. The Kn2000 was great for its time. The Kn3000 was about fair. The Kn5000 made a big jump. The Kn6000 gave me six months of problems; they gave me a new Kn6500 without charge. I feel that the Kn600 and the Kn6500 fits into the same category as the S970 and the S975, a small improvement. There are many here who would have bought a Kn8000 without thinking of how much the upgrade was.
My point; I did not question the upgrade, I just bought the new model because of their past reputation, knowing they had not failed me yet. And since I owned the S970 and the S975, I say there was enough of a difference to warrant spending the money. What else gives me the pleasure and joy than getting a new keyboard?
OT. Gary has taught me that when you stay with one make keyboard, you add more to what you already know. That means you get to explore the keyboard to a greater depth. Gary and Fran come to mind. If dollars are not an issue, buy every new model as soon as it comes out.
Just saying, John C.