The NH-U9 is a great example of a heatsink that can be used for either efficiency or quiet computing. It's made of intersecting fins of aluminium, which afford a maximum surface area for heat loss. This allows the NH-U12 to be used as a passive heatsink for chips with low TDP, but attach an optional 120mm fan and you get a highly efficient cooling setup.
The heatsink is so tall that unless both it and your motherboard are securely fastened to the case, the sheer weight can pull hard on your CPU socket, damaging your computer. Our Pentium D chip produced too much heat for us to run the NH-U12 passively, but by attaching a 120mm fan it was slightly more efficient than the Fatal1ty.
We would recommend the Noctua: it's more efficient for the price range and has the option of running passively, if your processor has a low enough TDP. Orestis Bastounis