Our shop has a Haas GR 408 gantry. We don't do any granite so I can't speak on that issue but I can about the gantry. We bought ours primarily due to the table travels (50x100). We looked at 4 other gantry style machines but the Haas beat them out in every respect (heavy duty contruction and stability).
We offline program ours and has worked great. We do developmental (R&D)
3d work. Cost was around $90 thous. I suggest going to haascnc.com and check them out. All the specs and cost available there.