The stock heatsinks on AMD's processors are just fine, and the higher end heat sink with the copper heat pipes actually works really well for overclocking when paired with lower wattage AMD chips. I've never had a problem with their heatsinks, but I'm currently running all aftermarket sinks because I overclock and they're quieter.
Stock heatsinks are fine for stock processor speeds, and even mild overclocks. There are what, about 4 billion of them out there working just fine? Unless you are planning on more advanced overclocking, buying aftermarket heatsinks is more of a money making racket than anything.
Now I am sure someone is going to pop in and say, "well my CPU was running at 60c before I changed to the hyperfrostomatic 12,000, now it peaks at 54c." I say to that, so what? What was wrong with your CPU running at 60c? Its still going to last longer than you will be alive, and it wasn't really causing any problems, was it?
There is a time for a good after market heatsink, but in 15 years of overclocking like 10-20%, I have never needed one.