Ian- I might be wrong on this one, but when the PSR-S910 was announced, I read some reviews saying that it is not a must have upgrade over the 3K. It still might be a leap, but not as big as the S950 (from what I'm reading right now). So I don't think I'll upgrade to S910 / S750.

Gary- I didn't mention the price, because here in Israel we have no options. I kinda have to buy from the local Yamaha dealer, because buying a used KB off eBay will cost a lot of money (taxes) and in that price I could buy a new KB with warranty. Otherwise, I would have bought a used one long ago.
But saying that the sound quality is far superior is convincing me (-:

The ultimate test for me: if I'll still want one next week, I'll probably buy it (-: