We've added preliminary renders of how (half of) X3 will look like.
Using a 2U case would require to have some air tunnels. This would have meant that we would have had a case of 1400 x 450 x 89 mm = 56070000 mm^2.
We understand that not all customer have deep racks or space therefore we've opted for the best solution to save space.
X3 will now be 2 x 3U: 450 x 180 x 133 x 2 = 13446000 mm^2
This is 4.17 times smaller than the previous solution and a lot more silent.

More pictures here:
http://www.blackarrowsoftware.com/store/prospero-x-3.html