Thank you all for your info.
I've decided to go for the rack version instead as I found out I have a Korg Z1 Voice Expansion Board, so it would be a real shame to sell it when I would like to get a Z1 (was thinking wether I should think about the EXB-MOSS instead of the Z1, but now it's clear the Z1 is the way to go ).
Getting a Z1 I wouldn't have enough room for the K5000S.
So now I would like to know what kind of knob box should I use if I can't get it with the macro control box from Kawai?
Also, what would be a fair price for a K5000R?
Thanks in advance