Hi Deanne,
no really, it's actually based on the PA3X without all the bells & whistles.
http://www.sonicstate.com/news/2012/09/05/-new-korg-arranger-keyboards/PA500 was based on the PA800/PA2x.
KMA really is sort of unique.
Unlike Yamaha , Korg appear to bring out the Top of Line arranger first, then the mid level arranger a year or so later, wheras Yammie put NEW features into the mid level PSR's first, then bring out the top of the Line arranger.
Copy the last link and paste it in Google Chrome and translate it.
On a very quick look it doesn't seem to be much different than my KMA except
for key size and the songbook.
Deane