Since it's already announced I can break my silence; there is no real difference between the 809 and 909, *except* updated songs (they're much more contemporary), the half damper feels *much* better, and the LED's are now blue and white instead of red and green to aid the colourblind. Oh and although I've tried both 809 and 909, I didn't have them side by side so I didn't notice if there were *any* differences in the speakers.
Both already used the CLP785 samples. They even have identical style and voice libraries. But you can't order more 809's... for example we're out of polished white, and down to 1 PE 809 left, we can't order more (we've asked). So from here on it's 909 or bust.
Mike, I can tell you a lot of differences between the CVP805 and 705, but since the 705 served your purpose, does it matter? But in a nutshell, the 805 has one more dynamic velocity layer over the 705 (both pianos sound great though), the 705 has great ensemble strings (same as the 805) but the 805 has sampled solo strings (viola, cello) where the 705 does not. The 805 has revo compatible drums, the 705 does not. And the 805 has a lot of extra jazz scat vocal samples (and gospel 'shout outs') that the 705 does not. The 805 has the ultra wide twin guitar the 705 does not.
That's 90% of the differences, the rest being extra brass/horns and woodwinds/saxes.
FWIW, for me? The only differences that I would utilize are the solo cellos, and revo compatible drums, the twin guitar sounds, and of course the slightly better piano.
*update* after trying them side by side (briefly before all 809's uprights sold out here, we still have 2 809GP's though); turns out the 909 cfx piano isn't quite as good as the 809 one (the difference is very slight) but the 909 Bosendorfer is slightly better than the 809 Bosendorfer. All other sounds come from the Genos. So other than a slight difference in VRM between the 2, all the GEnos voices are the same (indeed, the registrations are identical, and can be used back and forth) the only other differences are blue and orange lights (instead of red & green) and the new half damper on the 909 (which is nice); oh but they also added full Smart Pianist support to the 909, which is also nice (they 809 could use smart pianist, but they didn't bother with the light up keys via the app since the piano already had that feature on board).
Mark