first of all your build is messed up. the 6770 would be the bottleneck to your i5 3570k since its super low in terms of GPU performance. your rig would be faster if you used a i3 3220 and a 7850 over a i5 and a 6770.
now to the case, i suggest the antec 302. great build quality, has usb3, and is only 55 bucks. very good bang for the buck
spending 100 dollars on your case and not spending enough money on your GPU would be a dumb thing to do. my recommendation is at least a 7850 for games
I already have the 6770 and the rest of the system is a upgrade. I am planning to upgrade the gpu but currently I have limitations with the C2D e7500 and most games I play.
Back on to the subject in manner, I found problems with the HAF case and the Overseer I decided looks weird so I was leaning towards the 500r which I will be getting later this year thanks.