It will fit with most cases to be honest mate.
I've got one in my Zalman Z9 Plus, which is a £45 case. So don't feel you have to splash out all that money on a top end case. Albeit, the 800D and 650D are beautiful specimens.
Basically all it requires for the H50 is a place to hook up a 120mm that is not too far away from the CPU socket. Some people put two 120mm fans on the radiator though for a push/pull configuration which is supposed to help drop temperatures a few degrees extra.
Have a look at my build thread here:
http://forums.overclockers.co.uk/showthread.php?t=18288208
That will show you what I done, and is also an example of a push/pull configuration.
Also, when installing the H50 with two fans attached, if your motherboard requires a a power connector at the top left behind where the H50 will be situated, be sure to plug it in first and run your cables before installing the second fan on the H50 radiator otherwise you'll only end up having to remove it again anyway.
EDIT:
Also see here, the guy has one in an Antec 300 with a single 120mm fan
The latest pic of inside my case, hard to take as its under my desk and a bit of a squeeze