your i5 2400 WILL NOT bottle neck the gtx 650, infact if you have a little extra grab a gtx 660. you might start bottlenecking in higher end cards, but it would be very minor, and it would have to be like a gtx 690, maybe 680 but i still think your fine with a 680.
and the motherboard could be a little nicer but as long as it holds up you'll be fine.
The 650ti is an improvement on the 550ti but not by a huge ammount. An SSD will only help with load times and file transfer times, it has little effect on gaming (bar loading intervals).
You might be able to get a 3rd generation i5 if you have the second revision of that motherboard.
If you just wanting a bit more FPS then perhaps the graphics card and some 1600mhz ram but to be fair if the PC is doing what you want right now i would save up that cash for the next lot of CPUs.
A 560ti. It's a no brainer, you can find a used/refurb for around the same as a 650ti, but the 560ti competes with all the midrange GPUs from this generation,