Yeh, this is a dilemma! I'd say try the stock HSF and if you're not happy with the results get the best alternative your research turns up. AMD CPUs are extremely reliable so you shouldn't have a problem in three years.
But there is a "best of both worlds" solution - hang on to the AMD HSF just in case. If you do have a problem, send it back with the CPU when you RMA. It's not being dishonest, you chose a great 3rd party unit, didn't you?
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