Very impressive indeed!
I have a show later this year that's going to have an overall image size of 26,880 x 1080 (14x 1920x1080) pixels
roughly a 350' wide panoramic projection...making the content is a pain in the ass! haha
good to know I'll be able to do it off the 680s, as my servers will be sitting with a pair a piece (4 gig version), each server handling a different 'side' of the projection with control monitors for each server, so add another 3840x1080 pixels being pushed out of the servers