not sure if this is the right sections, but i just put together my new i7 920 build with the dark knight heatsink. it's idling about 39ºc and when i play games or it's under load it hits about 55º. that's with the turbo mode on and it's at 2.8mhz.
Also, how did you apply your thermal compound? It will play a factor in your temps as well, since the DK requires a unique method versus the dot method. Here is a good thread on how to install the thermal compound... http://www.tomshardware.com/forum/ [...] e-xigmatek
Overall, your temps are fine but I would review what xaira and I've stated to see if you can drop them down some, since you should be running cooler (depending on ambient temp)
There are 101 variables, however, idle temperatures are much less significant than load temperatures. Prime 95 Small FFT's is the Standard for thermal testing, so in order to draw any valid conclusions, please run the test for 10 minutes while monitoring with Real Temp, then report your findings. Make sure all fans are at 100% RPM, and air flow is not restricted, such as in a desk enclosure.