I've been running this server hardware for a bit (shoutout to serverbuilds.net) and recently decided that since every other computer I have is water cooled, this should be as well. It was running dual E5620 but that felt really ridiculous to water cool, so I was able to secure a pair of X5670's off eBay for like $40 total. The X5670's have just under double the passmark score of the E5620s and actually consumed power/put out any heat.
With this set up, the CPUs run room temp idle, average about 35C (+10C from ambient) and max out at 60C under sustained 100% load. Something fun I found out while stress testing the CPUs is just how inadequate the cooling is for the Northbridge (since it's designed for a 1U server chasis), as about 15 minutes in to the test the machine shut off because the Northbridge was about 115C. Whoops! I don't think this will ever happen under real circumstances, so I'm gonna do nothing and if it ends up being a problem I can probably just stick a fan on the side panel which would point it directly at the Northbridge and call it a day.