Here is a link to a very good web site with more useful information about cpu heatsinks that will help you make an informed decision: http://www.frostytech.com/top5heatsinks.cfm
Scroll down the page to see the AMD compatible cpu heatsinks.
You can use the Google embedded search feature at the web site to find more information about heatsinks for specific cpu sockets.
Personally I would recommend the Coolermaster Hyper 212+. The heatsink pretty much represents the best bang for the buck. If you shop around you can usually find it on sale for $29.99:http://www.newegg.com/Product/Product.aspx?Item=N82E16835103065&Tpk=cooler%20master%20hyper%20212%20plus