thats a good case, my son has it! I do not like case setups where one air current is fighting another, the old wind tunnel has been going for years and works! You should have another push air fan at the front.
Normal 2 blowing in and 1 sucking out in the same direction.
And as others have said , try and lower vt, bit by bit, maybe you can get the same Mhz at a lower vt.
I know people will say different - I put a pea size or even less, then I use a cut down credit card and gently scrape the mass over my cpu. You are filling imperfections on the die and heatsink, holes we cannot see. I have used this method on so many builds, because i get better results. Its as much metal to metal that gives best temps, not a sandwich layer, i.e metal - paste - metal