To Bruno123...

John - Yes, I imagine that I'd use all 3. I currently use MIDI, MP3 and Registrations, all 3 of these, on the KN-7000. I typically
get fairly "deep" once I choose a keyboard. I have added all kinds of stuff to my KN-7000 to get the kind of control I want - like a Peavey PC-1600x MIDI commander to call up registrations with one button press - and an external 2-1/2 octave MIDI controller as an "upper manual", and MIDI pedals for pedal playing (like an organ) - so my KN has become a centerpiece of a fairly complex rig.

I'd hope to eventually do the same with a Yamaha . . .

Thanks again,
Jim