The stock fans are horrible! I replaced the fans with 4 spare arctic fans i had spare.
http://www.memoryexpress.com/Products/MX49912Hope that helps! Got it down to 35dB.
Ps.: A new 8GB Image is ready, but i am on the road and will upload tonight.
I have 2THs version, so I used 8 pcs Sunon HAC0251S4-000U-A99 which are good quality, very quiet and very cheap (about USD4/pc), noise is less than 30dB and my temperatures are less than 50C. It is very similar noise to desktop computer.
Cheap and easy way is to use USD1/pc DC-DC buck converter from ebay which can lower voltage of original fans, but they are still a bit noisy even at lowest speed.