There is no such thing as CPU bottleneck the GPU.
There are applications that use more CPU or more GPU.
You will get much better FPS on highest settings with 1070 than with 760.
But your GPU will not be utilized for 100%.
If you plan to upgrade your CPU within a year, than 1070 is a good choice if you want everything maxed out over 60FPS on 1080p monitor.
Also 500w psu is meaningless, they are not made equal. A model is required to tell if it's good or not.
Also RX 480 coming out in 3 days is worth to look at.