Stick with the twinFozr and 'super overclock' it yourself. The cooling can handle it. Either case is fine, but I'd suggest the lian-li k58 or CM920. If you want the ricey-ness of the HAF cases, either is fine, cases don't really effect performance.
You might want to get something more beefy than a CM 212+ for cooling if you're into overclocking though. Most of this is just opinion. Your core components all seem fine.