I would seriously consider the Microarranger as a controller and sound source with the Midjay Plus. I've always liked the Korg sounds, and the styles and SMF playback of the Ketron. I've happily used the Midjay Plus/PA800 combo for a couple of years. The combo is a good match and allows me to have a back up to the MJ under my finger tips as wall as a good deal variety when I need it. Although the Midjay is my main piece, I do use many of the Korg styles on a regular basis.
Ciao,
Jerry