Also don't waste your money on getting the Corsair SP120 fans. While they are quiter than the Noctua's the temps will rise over 60c pretty much %100 of the time.
Which is absolutely fine, that's the same as an S5 in 35-40C ambients. SP120s are the quietest you can get an S5 - within reasonable bounds.
Using two SP120's temps rose to 65c right away, and it was cool in my house. Soon as the warmer months come that S5 will fry up. Used two Noctua 3000 and temps were 10c less in same room. Nothing special at all about the Corsairs.
As I said before, 65C is fine which you can improve by taping the top and bottom of the heatsinks closed. SP120s are quieter than the 3000's but slower, because that's the speed they're designed to run at. Neither fan is "better" than the other - they're just different.
They are sitting on a flat surface already. I guess I can try taping the bottom and top heatsinks and see what happens. I do like to keep them running at 60 or below, since we really don't know the real temp of the ASIC chips. Do you know the max temps of the ASIC chips on there? The sustained temp?