Delta Fans

[kiara]

You do not want to use deltas unless you are housing the box in a datacenter or have some sort of noise cancellation.  Go with noctua's NF-12's instead.

i am not an expert in fans but why NF-12?
his fans run at 2000RPM, 


looking at http://noctua.at/en/products/fan

most of the NF12 series are below 2k rpm, only the  industrial ones are above 2k rpm, actualy only 2 of them has higher RPM than his.