I'm surprised that no one here mentioned the Grand Piano expansion board for the Yamaha 9000 Pro. Has anyone here ever tried it? More to the point, has anyone here tried it and liked the original 9000 Pro stock piano sound better? According to the posts I have researched, those who have tried the piano expansion board prefered it over the stock 9000 Pro piano sound. Since you guys like the 9000 Pro piano sound so much, I just thought maybe someone would say if the expansion board is even better, since the question was about what has the best piano sound...