It will perform better than an FX-4100 as it can better spread background applications and tasks around so they don't get in the way of the game's processing. It won't be a monstrous gain as even the FX-8350 can struggle to support higher framerates and high end video card setups.
Most games I've come across show the FX-8350 performing better than the FX-6300 even when they don't use all 8 cores. So if you overclock your FX-8300 to 4GHz it should perform pretty well.