So far a little bit vague about polyphony. Hope that there's at least 128 voices for common sounds like piano. It won't be the first time when Yamaha turns a keyboard into a toy by reducing the polyphony quite ruthlessly (for example, MM6).

But 76-keys version is a change. It used to be only 61 or 88 for a MM, MX, MOX and MOXF.