Sadly,no. You will need a more powerful CPU/GPU in order to see an increase in fps. A case is nothing more than a metal box which holds your components.
It would not increase your FPS directly. The only reason it would increase your FPS is if your parts are being throttled. Which means your speeds are slowed down to prevent them from EXPLODING or simply over heating. Short answer, no, unless you upgrade your PC specs.
I might upgrade my case because I heard it can get you higher frame rate. I really need a better frame rate because my gts 240 just doesn't cut it.
Ummmmmm....... Really?? You believe that!!! Not trying to be rude but how in the world would that even make some sort of sense??? NO it will not increase frame rate