If you want to play games with a discrete there really is no point in getting an APU. The APU is good enough if you are going to use the integrated graphics but if you want to use a discrete video card I would avoid the APU as the weak CPU core will bottleneck high end video cards.
I'm sorry I don't understand. Will it increase my FPS and be able to play on higher settings?
No. The APU has a weak CPU core and will bottleneck something like a 660 or higher.
Yep, APU's are generally designed for people who does not have any plans in getting discrete cards. But then again, you should have a decent frame rate it's just that .. You will not get the "fullest" power of the GTX 660