I used the Yamaha S-YXG50, Edirol Hyper Canvas, Prodipe VE and Coyote ForteDXi I used with OMB. All GM and GM2 compatible and the old Yamaha sounded the best. But you know I am a big Korg fan and I bought my PA500 for only 900 Euro. The MS cost 2900 Euro excl tax. You can't beat the Korg there. Just as the Ketron Audya I find the MS way overpriced.