Well, any AM3/AM2 cooler will work, although I'm not sure if it'd be able to get the original Phenom X4 9850 to 3.4 GHz or so. The best that I know of is the Thermalright Venomous-X or Noctua NH-D14. The Venomous-X does not come with an AM2 installation kit so you will need to buy one instead.