When it comes to Xeon server motherboards you're fairly limited when it comes to coolers. Just as well then, that the Intel STS100C is a good solution; I installed one of these in our new virtualisation server on a Supermicro board with a Xeon E5620 and it runs exceptionally cool under load even with the fan set to a lower speed. If you need it any cooler though, crank the fan speed up and it really comes into its own; it sounds like a model aircraft, but then this is a server solution so you're not exactly going to be running one of these things in your average living room, bedroom or study.
Installing it was dead easy and it comes with thermal paste on it. For under £25, you won't find a better Xeon cooler.