How much are you willing to spend? The GPU upgrade will help a lot but yes, i agree with qwertymac93, the PSU you have will desperately need to be able to carry more power. If you're going midrange, a gtx 560ti will probably do you good. Try this on for size.
For the CPU, you have a socket 1156 so I would recommend something like this.
You should probably try to offload the 650 you currently have to make up some cost if you're seriously going to do this upgrade though. The 750 is a quad core and the hyperthreading of the 650 won't make up for the raw power of the 750 with its 2 extra cores.
The case you have is a little cramped but if you can clear it, the hyper 212+ is very highly rated and is a very reasonable price. You would definitely have to make sure the hyper will clear your case though.
Grand total for an upgrade like this is $30+$225+$215 so you're looking at $470. A bit rough. Going back to the PSU issue though, if you're running an i5 750 AND a gtx 560 Ti, you would also need something like this.
That tacks on another 85 so now you're at $555
The items themselves are good, but not cheap as you can see.