If you have a rev 2 mobo there you can put 6 core westmere chips (just did this on a office machine) They can be had cheap and are known to OC well past 4ghz (sometimes even 5ghz) - If your board is not updated for westmere EVGA also does factory updates for it for $50 - http://www.ebay.com/itm/Intel-Xeon-X5650-2-66GHz-Six-Core-12M-Processor-LGA1366-SLBV3-/111962034719?hash=item1a1175121f:g:L-YAAOSwiylXB2QJ