Well considering you only have choices between Casio, Yamaha, and Korg...with Ketron's Audya still in development, and the Mediastaion not really an arranger...I'd say Korg would probably have more of a chance in filling your requirements (Yamaha's lack of 76 being the main reason for exclusion).

Personally, I wouldn't want half of those features...it would take away from the fun of actually playing, and put the instrument somewhere between a big musical toy, a Karaoke machine, and an over-sized I-Pod.

What next..a built in cell phone?

Let's see...

Great sounds (and effects).

Flexible OS.

Great styles.

Great style creator.

Great third party support.

Light weight.

Reputable company.

Hey, I already have all those...PSR-S910.

Ian