Sorry I'm late to the party on this thread but I have to piggyback off of Don's comment. I made a stink about the missing "three keys" mode on the PA600 board over at Korg Forums. Paolo Trammanoni acknowledged my objections and asked me to elaborate. I did my best, but when the PA900 came out it was set up the same way: no "Fingered 2" nor "Fingered 3" modes. Just a weird Expert mode that's something like Yamaha's AI Fingered, but IMO, not as thoughtfully executed.

You can almost guarantee the Pa4X will follow this pattern. You might be able to fake the board out by adding a 2nd manual and/or BK-7m, but a strong point of the Pa3x was its completeness, obviating the need for extra gear.

Chord recognition and style engine are the defining features, the sine qua non of arrangers. Because of the missing modes, If I ever replace my Pa800 I would get Pa3X, or just downgrade to a Pa50 which are plentiful in the second-hand market. Ironically even the $400 Micro has the missing modes. What is Korg thinking??