Rikki,
There is only one midjay model but you can have it equiped with different options. You can get it with or without a vocal harmonizer. When I received my last shipment about 3 weeks ago from New York, they all had version 2. Version 3 would be an update. I would also suggest that if you want a better style player to go along with your digital piano, I would suggest looking into the XD3 module. It is quite a bit larger and it doesn't play mp3 or wave files, but for style playback and quick minipulation, it tends to sell better than the midjay for mostly style use. It also is a bit less expensive by a few hundred dollars. It can also be bought with or without a hard drive (floppy only) and with or without a vocal harmonizer.
George Kaye
Kaye's Music Scene
Reseda, California