For a budget of not more than US$1,500 - Yamaha S80, you can add 2 synth expansion boards later. It has decent piano sounds plus good master controller features.

For a budget of not more than US$2,600 - Roland XV-88, you get very good piano and synth sounds plus expansion capability from Roland's huge sound board library.

I am not familiar with GEM's RealPiano Pro2, so no comments on it. It looks very promising on specifications if you focus on piano sounds mainly.

Paul Ip
from Texas