I tried NH-D15 and several other coolers on my 3600. Ended up sticking with Thermalright ARO-M14O (same as ARO-M14G Gray top but with Orange top). Not hard to find but very good and quiet. It's 1-2c warmer than D15, but 3dB quieter and £20 cheaper is good enough reasoning for me.
I know answer is over a year late, but here it is.Is the ARO-M14O the same as the Macho 140 revB but just a orange top? Loved my Macho, such a quiet cooler and almost half the price of the Noctua!