This is the GeneralMusic forum: GEM, which is an Itallian company like Yamaha, Korg, Solton. To get the best answer, please repost your question in the topmost forum.
But since you are here, let me tell what your options are:
1-GEM realpiano module, based GEM realpiano1. It is ok. Realpiano2 is way better. But they do not make realpiano2 module unfortunately.
2-Yamaha MU128, very good sound and very good price... only if you like it. I wish they make Yamaha P80 module.
3-Roland XV1010, good piano, very good price. I am waiting for it go even lower and then I might get one.
4-Roland XV3080, better piano, very bad price. Cut it in half and I will get it now *smile*
5-Kurzweil micropiano... ok
6- Proteus2000, I never heard the piano sound in it. But some people like it.
I have this is helpful