Replacing the fan in ReadyNAS Duo - possible?

I seem to have a very high pitched noise emitting from the Readynas Duo and it took me a while to track it down to the NAS. It is so high pitched my wife says she cant hear it and the kids havent moaned about it but it is driving me mad, my ears are still ringing an hour after i turn the NAS off (put my hands on my ears and i can hear it so its nothing in the room still!!). It has only just started this noise though.

Traced it to either the fan or some electronics in the NAS but on disconnection of the fan and powering the NAS up briefly (drives also removed to make sure they werent the noise source) it was silent so it must be the fan. Seems to make the same noise no matter the RPM of the fan.

So i'm going to try the Fractal Designs fan, there is an R2 version now which i dont think the other people in this thread were using?
R2 - http://fractal-design.com/?view=product&category=4&prod=75
Other - http://fractal-design.com/?view=product&category=4&prod=15

It has a higher CFM and a lower dB than the other one mentioned in this thread.

I will update the thread once i've got the fan and tried it out.