In our noise level tests we switched off all the case fans and replaced the AMD Radeon HD 7950 graphics card with a HD 5550 passive model so were just taking into account the noise generated by the cooler fans themselves.
We measured the noise level with a Digital Noise Level meter at a distance of 1 m from the front of the system.
From above we can deduce that all five configurations are very quiet, with three registering under the minimum 30 dBA sensitivity on our equipment. Out of the five, we would say that the Dark Rock 2 was the quietest. In fact we would quite happily describe it as silent.