first of all, you are fine using the stock cooler, otherwise amd wouldn't ship them out with the cpu
but honestly: the amd coolers are the crap of the crap
they sound like a jet engine and support you only with minimal cooling performance
as already said, the cooler master hyper 212 evo is a good one to get
it's really cheap (30 to 40 bucks) and it have proofed itself in the past with cooling-performance, noise-level and overclocking-headroom
definitely go with that
if you want something more exclusive and kind of "mind-blowing", go for the noctua nh-u12s
i use this cooler with my fx 8320 OC to 4.2ghz and it's really really good for its 120mm single-tower design
it also guarantees you 100% ram compability if you use/like ram with higher heatspreaders like I do
mentionable is that the noctua comes with a "nf-p12 pwn" fan, imho the fan to get atm for heatsinks and radiators
they are focused for air pressure, which you need for your heatsink and they are really really (yeah really) silent
I use two of them in push/pull and even at 100% fan speed, they are completely silent
the only little thing you can hear is the actual air itself being pushed through the heatsink