Disklavier

Hi

I want to upgrade my Disklavier MPX1Z which is a MKII piano to a 
MKIII. I believe that this can be done with a control box 
replacement. The current control unit is the DKC500RXG. What are my 
options? and where can I find out the specifications of the new 
control unit(s). Also where can I get the best deal for one? I am in 
the UK.

TIA & Happy Holidays.

Gary