Hi Mate,
I assume that you have covered off the basics. ie. The language displayed is firmware dependent. Is it apart of the firmware updates that are covered on the NAV DVD, or is it upgraded a different way.(or is it an eprom that needs to be replaced). You would have to assume that it would be a variable. These units are sold around the world and the only diff in manufacture would be firmware. Mate if you haven't researched it yet, I would. Regardless if you source a wrecked Is250, they will charge a premium for the unit!!!
(I guess the only thing I didn't consider was the screen printing on the buttons, not sure if that would justify $7K)
Let us all know how you go and if you know something different!!
Not sure I understand what you mean by "firmware". Both the buttons and sceen information are in Japanese ( except song titles!) . IT is an HDD systems so an English disk can't be inserted to convert it
