Yamaha does not make a keyboard for under $400 that includes mega voices. The megavoices were introduced with the Tyros, and then added to the PSR-3000. Where did you find the 6mb's for the Casio? I'm curious because this info isn't listed in the manual, nor have I been able to find it anywhere on the net. I even emailed Casio and got no response. I still say the WK-3000 or 3500 is a good board to have in your price range.