sorry if this is already asked but im concerned about the performance, it all works but i dont feel like the 760 ti is giving its full power, is the 560 lowering it down or what can it be? shall i take it out and leave just the 760ti
If you are using the two cards in sli, the performance will be gated by the one with the slower specs.
I might suggest selling both in favor of a single stronger card. You will avoid stuttering and tearing issues.
If you are using the cards independently for attaching extra monitors, there should be no performance conflict. Even then attaching extra monitors to your gaming card makes no real difference in performance.
You cannot SLI a GTX 760 Ti (OEM) and a GTX 560 Ti. You can use the GTX 760 Ti (OEM) as your main card and the GTX 560 Ti as a dedicated PhysX card.
Other than that your system will choose one of the two cards to use during graphic intensive applications. Which by your description is probably the 560 Ti. You'll have to set up a main card and a PhysX-only card through the Geforce control panel. Once done, you should notice a drastic increase in performance going from the 560 Ti to the 760 Ti (OEM) - which is essentially a rebranded GTX 670.