If I had my druthers and I had to do it all over again, instead of buying an arranger keyboard, as a professional pianist, I would opt for an 88 note weighted keyboard and MIDI it to a Ketron arranger module. Best of both worlds.
Mark
If they ever release an SD9 module... i would midi it to an 88 key Korg Kronos, Yamaha montage or a Roland RD2000. That would be indeed a great solution..
But whats wrong with integrating the Tyros and the Montage into a single instrument?
Once uppon a long time ago GEM did this into their SK880, it was an 88 key stagepiano, a synthesizer, a workstation and an arranger at the same time, all high emd of the spectrum. I have been wayting for a good replacement ever since, but nothing was released.. for my playstyle, 88 weighted keys offer a much better performance then synth/organ keys.