erm, so far for my sapphire r9 290, fan speed did give some impact in my case, didn't use overdrive since first day, but i tried on overdrive just now, set the temp target to 80c, and try run valley:
» Click to show Spoiler - click again to hide... «
Overdrive (target temp 80c):

Temp running the valley: (Temp stable at 80c but throttling appear)

Valley result:
https://dl.dropboxusercontent.com/u/2923116...0%28Copy%29.pngHowever, my current setting is using custom fan profile from AB, temp max at 76c with no throttling
» Click to show Spoiler - click again to hide... «
AB fan profile:

Temp running the valley: (max at 76c and maintain 947mhz)

Valley result:
https://dl.dropboxusercontent.com/u/2923116...0%28Copy%29.pngi even tried to OC to 1077/1350 with custom fan profile, temp max at 76c with no throttling
» Click to show Spoiler - click again to hide... «
but i end up with 70%+++ fan speed which is super loud, cheers

Mind to tell where u download the msi afterburner? I saw your voltage can be adjusted but mine cant