I was planning on the same thing...I know I have seen a pic with the Tuniq next to a ruler, but couldn't find it for you. I did find this article that
This is what they said:
"The Tower 120 is a mighty beast. It is 15.5 cm high, and it needs at least a case with 19 cm height. Tuniq claims it is compatible with most cases and motherboards, and since it did fit in my smaller Antec LANBoy case I’m sure it is true."http://www.bjorn3d.com/read_pf.php?cID=812
So if you don't like metric that makes the tower a little over 6" and the necessary dimension around 7.5" The 900 case is only 8.1" wide, so it looks like might be a tight fit.
Most people I have talked to have thought it should. Let us know how it goes (I am planning on one when I build my new computer in late July)