I do about 2 upgrades a month using X5680's and X5690's, as ilikewhey stated above it is a sales ploy to get extra money. I get these processors from Dell and HP servers and even when I don't use the same matching pair that came from the same server there is no difference in performance. Look around for X5680's at around $45 to $50 and X5690's $75 to $85. These are not hard to find but some sellers charge extra due to the knowledge that Mac Pro owners will pay too much.