I believe I was told that most of the Yamaha's have a 'mirror input' mode for the MIDI in, where all the layout for the arranger's keyboard (sounds, splits, etc.) are mirrored onto a single channel MIDI input, so if you have a particular preference for say an S900 or S910, or even the T3/T2, you could buy a dumb 88 controller (a nice Fatar action, e.g.) and place the arranger just above it (in REAL close as you won't need to touch the 88's knobs, or see it's display) and you have your 88 arranger. Especially with an S900/910 and an inexpensive 88, you have the potential for something as good as many of the Clavinova's, at a fraction of the price... (oh, and a plastic action for those organ parts, too )