Looks like your case comes with a 120mm fan up top and a 120mm on the back. There are a lot of different ways you could arrange things, but personally, I think I would put the H100i on the top as exhaust and move the top 120mm fan to the front of the case as intake. And yeah, I'd probably want another 120mm up front for intake as well. Your CPU cooler will do a good job of keeping your CPU cool, but when overclocking you also want to keep your motherboard, especially the VRMs cool as well. I get the impression you're really wanting a solid overclock. If that's the case, I'd definitely recommend adding a second 120mm to the front.