I have the NOCTUA NH-U12P SE2 (replaces the NOCTUA NH-U12P SE1366) and I am pleased. At 4.0Ghz, full Prime95 load, 68*F ambient I run cores at 72c.
There are "better" heatsinks rated by performance. I highly value that the Noctua is quiet (I can barely hear its two fans on full), its high quality and I can get it at NewEgg or Amazon.
You can read reviews at FrostyTech
A cooler performance comparison is here