You have plenty of ram, and it should be operating in dual channel mode.
CPU-Z will confirm that.
The question is do you need a cpu upgrade or a graphics upgrade?
Run YOUR games, but lower your resolution and eye candy.
If your FPS increases, it indicates that your cpu is strong enough to drive a better graphics configuration.
If your FPS stays the same, you are likely more cpu limited.
If you are cpu limited, one upgrade would be to buy a Z170 or Z270 based motherboard so you can overclock your 6600K. Now. your peak is around 3.6
With a good overclock, you should be able to get to 4.5.
If you need more, you are looking at a 9th gen processor like a i5-9600K which will get near 5.0.
That will also require a Z390 based motherboard