Fit a 360x120 radiator with three 120mm fans, blowing air from the cabinet out through the radiator. Should be OK for dual Xeons, if you do not overclock them. I have one quad-core at 3,6Ghz, and a 240x120 radiator. With slow speed fans (1000rpm) the load temp of the cores is 55-60 degrees Celsius. Put quality waterblocks on the Xeons, and a quality water pump. Use 1/2" tubing. Few things beat water when it comes to effective cooling.