The heat pipes are reliable they can dissipate the heat, the weakest link is the fans. The D15 is warranted for 6 years but if both fans die then so does your CPU. I would rather have the D15 in there as opposed to a stock cpu cooler.
Why don't you run a water cooler and and then you don't have to worry about the bulky heavy D15's overhang. I like the Fractal myself. The 140's are nice and you will get use to the noise. I have an old Azza Hurrican loaded with stock fans and it is noisy but I am used to it.