Sergey, did you mean that 120mm fans were 5°C warmer than a single 140mm fan and 3-4°C warmer when used in pairs compared to 2x 140mm fans?
For Part 2, can you also include 2 other CPU cooling products that consumers who are looking at Noctua NH-D14 and HR-02 are likely going to consider.
The first one is the newly released Thermalright Silver Arrow. It retails for $79.99 but already comes with 2x140 mm ultra quiet fans - http://www.svc.com/silverarrow.html
The second one is the newly released Corsair H70 - http://www.corsair.com/products/h70/default.aspx
Since HR-02 ships without any fans, once you factor the cost of the fans, H70 becomes a competitor.
"We decided not go for Noctua’s default fans for a reason that will be explained in our next article."
I think you should include the results anyways because I imagine most users will NOT substitute the fans on the Noctua as it already ships with stock fans.
A comparison of how noisy the Noctua vs. Thermalright fans are would also be interesting.