They are compatible - I have a Xeon 3210 in an EVGA 680i. They are good clockers aswell, got mine up to 2.8 Ghz with about 5 seconds work. Runs perfectly using 1.28v and cores idling around 39c using zalman 9700.
Well from my experience as I mentioned the Xeons clock very easily using low voltages and producing less heat. Supposedly because server chips like xeons are made from a higher grade silicon due to the stresses of the server environment.