All Yamahas...

PSR-510: Cute little keyboard that lit up like a Christmas tree when you turned it on.

PSR-4000: The 8000's little cousin. Especially loved the wheels beneath the screen. Yamaha replaced them with buttons in later models. Not sure why.

PSR-9000.

9000 PRO: By FAR the best key action I've felt on any keyboard I've ever played. Still my favorite of all offerings on the market today.

Don