I doubt it would fit, since a 2U case is only 3.5" tall, and 2U heatsinks aren't very tall. From that, you have to subtract the height of the standoffs, the height of the socket and processor, before you know how much room you have left for the heatsink and fan. newegg sells a 2U heatsink that's supposed to be good for up to a Q6700, though:
http://www.newegg.com/Product/...x?Item=N82E16835114066 I never thought I'd see a server heatsink with heatpipes, but I've seen one now.
