You might want to consider some typhoon's insted, if you need more air pressure 
I heard about them, but I couldn't source them easily.
Noctua are 1200 rpm ; are the Typhoons really more effective ?
Ebay is your friend:
http://www.ebay.com/itm/Scythe-Gentle-Typhoon-120mm-3000-RPM-Cooling-Fan-D1225C12B7AP-29-/371007811330?pt=UK_Computing_Case_Fans&hash=item5661c9ef02
there are plenty