You will still get higher framerates from the GPU. You will reach a point (especially at lower resolution/settings) where your GPU (thus framerate) may suffer because your CPU will bottleneck, but I don't think the GTX 770 will bottleneck your i5-3350p, at least not enough that you would get higher framerate with a 2500K and your 650 Ti.
The 2500K is around 10% faster (depending on overclock) that your CPU; while a GTX 770 is around 130% faster than your GPU. If anything, get the GPU first and if you feel you still need the CPU then get it.
Moving from one i5 to another on the same platform has never been a good way to improve performance. I would think that since you already have an i5, your next CPU upgrade would be a whole new platform.
What kind of power supply do you have? The GTX 770 recommends a 600W power supply as it pulls 230W of power by itself. So unless you already have a sufficient power supply, it may be just as cost efficient to get a GTX 970 and have better performance.