I just gotthe Haf 932 tower case, even though my PC is not overclocked _yet_ the case is extremley quite and cool, 2 big 240mm fans. One on the top and one on the side and a 120mm fan on the front make this very cool. infact it's a bit chilly in here!
Highly recommened and not thatmuch different to the HAF-X.
To be honest most "gaming" cases are suitable for a moderate overclock. On our configurator, the CoolerMaster CM690 and above will be fine - just pick one you like the look of and which fits within your budget