To be honest, and after having had one for eight years, I don't think I would put the G1000's piano sound up against most modern pianos. It IS a good sound, but first and foremost, it is a panned mono piano sound, not a true stereo sample, like the NP and YPGs. These, IMO, make for a far more realistic playing experience, a feeling of truly sitting down in front of a real piano (at least to a certain extent!) than any mono sample set.

Of course, with a G1000, you get a great keybed and a great arranger thrown in, but if the piano sound is your primary focus, I'm not so sure it would improve things for you.