Since you want more fps you should get a better gpu, keep the i5 2400 since it is still fine for gaming, try to get a rx 470, it's an amazinf boost over your current gtx 750. It should cost not more than if you upgrade to an i3 6100 (which will not give you more fps over the i5 2400, since the gtx 750 is not good enough)
The rx 470 will allow you to max out games at that resolution for years to come and will even be good for max settings at 1080p