The 750ti is much newer so even though it may be similar to the 560ti in benchmarks, it will have more features and is much more power efficient (I used to have a 560ti and it was a great card, but I bought that back in 2011).
That power supply is okay but is an older model - This is a newer, better unit and is a lot cheaper:
http://pcpartpicker.com/part/xfx-power-supply-p1550sxxb9You don't need all those fans at all - All you'll end up doing is making the PC very loud. Just get two fans - Put one in the front intaking and one in the back exhausting - That will provide more than enough cooling for the system and the money you save would cover a 750ti. The CPU also includes a cooler for itself so you don't need to buy a separate CPU cooler either.
You may also want to replace that board with one that supports USB 3.0 and SATA III.
I'd also strongly recommend getting a better case, that one you have will be very cheaply made - A better one will be quieter and easier to build in - They also often include fans from the factory.
Also consider getting two matched sticks of RAM rather than just a single one - This way they will run in Dual Channel mode which is faster.