The stock heatsink comes with (as far as I know) the same 21cfm slimline 60mm fan found on the other retail AMD coolers, but with a heatsink that has a copper insert in the base. You could replace that fan with a high-output fan to give yourself some headroom if you don't mind additional noise. If you want to pick up an aftermarket heatsink instead (or in addition), it sounds like AMD is calling for Thoroughbreds to be used
only with heatsinks that have a copper heatspreader in the base. The reason is that, although the new Tbred core produces a little less heat, it has a LOT less surface through which to transfer the heat to the heatsink.
That rules out both Coolermasters, which are all aluminum. The Globalwin SAK38 and CAKII-38 qualify (copper heatspreader or all-copper). The
Thermalright CB-6L appears to come in two styles but both have copper bases. Different fans though. The Vantec
6027D is pretty small but the 6035 looks all right. The Alpha is awesome but does not fit all motherboards, check
here for the fit list.
As listed, all of the candidates have loud fans. Because it takes an 80mm fan, the Alpha has more room to play with the noise-to-cooling ratio if you want to get some other fan for it.
Another couple of good candidates would be the Taisol with the copper base like
this one. or the Thermalright AX-7, which is about $25 without a fan. I guess I'll mention the good old Alpha PAL6035 and PEP66 as well, since they also have copper heatspreaders and take 60mm fans. The PEP66 calls for careful measuring to ensure that it'll fit, since it uses a side-firing fan instead of top-mounted, but it has good performance. The PAL6035 should fit absolutely anything unless it's height-restricted (eg, a BookPC or something odd like that).