For anyone that needs a good "add on" piano sound just like John's - I have a Roland SC33 available. It's basically the guts of his keyboard without the keys. It's a small tabletop unit with lots of group buttons for easy edits. Straight forward and simple - this will add 28 notes of polyphony with Sound Canvas quality ( VERY GM friendly!) to any midi keyboard. It also serves as an excellent sound source for computers with cheezy, or otherwise inadequate sound cards.
I'll post the price up in the For Sale section, if anyone is interrested.