It doesn't make sense that a GPU intensive ENB like RealVision to be mostly CPU bottlenecked. The 780 with a demanding enb such as RealVision (Full) doesn't have enough power to give 60 fps constant all the time. Overclocking the GPU might help increasing your fps. There are only four options, either to reduce ENB settings , to get rid of the ENB it completely, to overclock the GPU or to accept your current framerate. Overclocking your i5 4670K will not give you much increase as with the ENB you are mostly GPU limited anyway.
You can also try this in NVIDIA Control Panel which might decrease the input lag when fps goes below 60 fps.Warning: Spoiler! (Click to show)
Set Maximum Pre-renderd frames to "1" .