ClubIT has the s775 quad core Xeon X3220 (G0 stepping) for $294.99 + $4.99 shipping in stock. This is the Xeon equivalent to the Q6600, the biggest difference being the most excellent 85C T Junction (vs 72C on the G0 Q6600).
http://www.clubit.com/product_detail.cfm?itemno=CA1938011
http://www.clubit.com/product_detail.cfm?itemno=CA1938011