When buying an expensive CPU cooler make sure it has a good heatsink, not just a run-of-the-mill average heatsink getting good results because of a good 12cm or 14cm fan. You'll want to replace that fan (or, more likely, ans) yourself, in which case you should try them out before buying if at all possible, and if not, then buy from someone who offers liberal returns. Essentially, the stats on paper don't tell the whole story, even supposing they aren't inflated. Both the dBA rating and the type of bearing matters, as well as some other things, where a lot of noise can come from crossing air paths or vibration. Fans can be a good place to put your premium in, in terms of bang for the buck for cooling, since more blades, better angle, better shape and overall better design moves more air more quietly but is simply more expensive to make. But it's not normally horribly expensive, at least not in comparison to other cooling equipment.
You can still sell the stock fans if you want to and don't have a better use for them.