I don't understand these questions. You can always set a graphics card to lower settings so a graphics card will never bottleneck unless it's already running at the lowest possible settings.
The FX6300 at stock settings will drop below 60fps in some games. Overclocked it does better. But any i5 is still better. Will you notice? I'm not sure, it depends on what settings you have your 670 set to. If you set your 670 to settings it can't handle then it will bottleneck first. If you want to understand a CPU, take the GPU out of the equation and determine if you are willing to live with the FPS it can deliver.