Frosty Tech has lots of reviews. The Dark Knight seems a bit noisy though. If you go Noctua, get a NH-C14, it weighs a half pound less than the NH-D14 so is less stress on the motherboard with a bit better cooling. And it cools the motherboard better.
The Dark Knight is not as good as the Noctua NH D-14. I chose the Noctua NH C-14 and it does well for me, even though I only have an average CPU to overclock. I like how the NHC-14 blows on the motherboard to help cool components.
Some tests show the NH D-14 slightly beating the C-14 and some show the opposite.