Yesterday Sony put on event at Rule Boston Camera about their CineAlta cameras - especially the Sony PMW-F3 - and for the event they dragged along a digital projector. I believe it was the 4K DCinema Projector. This is a huge beast - about the size of an oven - and was probably much more than was needed for the comparatively small conference room we were in!
The images were impressive. This thing is clearly supposed to be installed in a separate room; the fans gave off a lot of noise, and it had a cute little tin hat on the top of it's ventilation spout at the back (normally it would be vented.)
Even though it was reportedly operating at it's dimmest (lowest?) setting, it was almost too bright; the image was so bright that in light images you could see the ripples and bends in the screen!
I don't think they sell these at Best Buy.
Sony: SRXR320P 4K DCinema Projector