I have yet to see any keyboard/controller/sound module that can faithfully reproduce a grand piano. Of course, I'm biased on the sounds because I have a 7'-2" grand in my studio.
So chasing that grand sound is going to be elusive.
I would suggest an 88 weighted key controller, something like the
Fatar SL-880 or 990 coupled with a nice Roland Sound Module like
the JV 2080 or 5080.
That way, for just under a grand, you have a nice keyboard, lots of sounds, and you can always add more modules. This allows you to continually add or upgrade your system.
If you don't like the idea of sound modules, you couls always go for a
Yamaha Motif but I don't think its quite as flexible as the individual components.
I have 2 Fatar keyboards. Both are 88 keys and weighted. Being a classically trained pianist, I like the action on the Fatar's.