The new Alesis keyboard looks like just what you need, and I've heard what it's capable of
on the SOS DVD last month. It sounds beautiful in the hands of the guy who played it on
that DVD. There are some less-good demos here on the Alesis website: http://www.fusionsynth.com/audiodemo.html
, but they still show you
what the Fusion can do, although there's some horrid generic rock on there (not my cup of
tea at all!).
The jazz piano demo is very nice though.