IT does make a difference and deffo worth doing (ECT should put this gas in anyways IMHO)
But I still put all my fans on turbo for benching at max overclock (272x13) but then back the clocks off so I can run 27/7 and set fans manually to 1800 rear speed and 1550 front speed which (at an ambient of 25 degrees) keep the mach unit nice and cool, quiet with good performance (usually I run at 250x13 on my FX55 for day to day stuff)
Mav