I just found out I can put a gtx 660 ti into a pci 2.0 slot and I am just trying to find out if I were to just swap out the cards would everything be alright? Also would it even be worth it I can play most of my games maxed. I think i fucked my self over getting the 560ti in the first place but im pretty confident I can sell it for 150$. Will it run good in a pci express 2.0 slot also? Thank you for your time and answers.
Go with the 660 Ti, single card options are always the way to go, it's cooler and quieter. You'll also want the 2GB of VRAM the 660 Ti offers to load high resolution textures (main reason I upgraded my 560Ti so I could run BF3 on Ultra). It will run just fine, 660 Ti's dont have enough memory bandwidth for a PCIe 3.0 slot to be much of a benefit, and PCIe is backwards compatible as you said so you should be good to go.
The 560ti came out in spring/summer 2011. 660ti was in summer 2012. Meaning.. you're only months away from new model.
I upgraded from 560ti to 660ti. I wanted Ultra and got it. I sold my 560ti and I lost $30. But got 3 months out of it. Totally worth it. 560ti is very capable and I would try to wait for new gen cards.