You can also run LGA 771 Xeons in LGA 775 with a mod ( http://www.delidded.com/lga-771-to-775-adapter/ ) They have a whole list of Xeon's that can be used and they overclock better and are cheaper than LGA 775 (IE: Q9650) I would stay away from the Q6600 cause it is 65nm and doesn't overclock as well as 45nm Core 2 cpu's.