The 7560D is integrated onto the AMD A8-5600k processor, meaning that if you buy that processor, you'll already have the graphics card (GPU) on it. However, if you're going to be building a computer with integrated graphics, you'll need slightly faster RAM such as 1866 MHz or faster. I would also recommend purchasing 4-8 Gigabytes of RAM. The reason is that with integrated graphics, the CPU and GPU share the same RAM, so faster RAM actually will make a difference in games.
The AMD A8-5600k is currently $109.99 on Newegg:
http://www.newegg.com/Product/Product.aspx?Item=N82E16819113281
As for performance, take a look at these benchmarks from different games:
Batman: Arkham City:
http://www.tomshardware.com/reviews/a10-5800k-a8-5600k-trinity-apu,3241-9.html
World of Warcraft: Cataclysm:
http://www.tomshardware.com/reviews/a10-5800k-a8-5600k-trinity-apu,3241-10.html
Skyrim:
http://www.tomshardware.com/reviews/a10-5800k-a8-5600k-trinity-apu,3241-11.html
Diablo III:
http://www.tomshardware.com/reviews/a10-5800k-a8-5600k-trinity-apu,3241-12.html
You'll need to Google some more 7560D benchmarks for the other games you mentioned.
For your last question, the GTX 650Ti is so much better than the 7560D. This page starts some benchmarks of the 650Ti Boost for some of the games you mentioned:
http://www.techspot.com/review/661-nvidia-geforce-gtx-650-ti-boost-sli/page2.html
If you have the money, I'd highly recommend purchasing the 650Ti Boost over the 7560D. If not, then buy the 7560D now, and maybe a few months later, buy a graphics card out of nVidia's new 700 series graphics cards, such as the 750Ti or 760 (which are not released yet, but will be before the end of this year).
Good luck!