I am looking forward to buying a Yamaha Motif ES6 (61 keys) - Can you explain what's the difference between Yamaha Motif 6 an Yamaha Motif ES6 ? I'd buy a new/used B quality - Right now i own a Casio WK-3500, a Roland VA-76 and i want a workstation ( Yamaha Motif ES ) but i want to know the difference between Motif 6 and Motif ES6