Yes you can run a quad core CPU. And yes you will be able to OC it if you go for a 1:1 ratio:
Q6600:
Multi x Actual FSB, Stated FSB, RAM Speed = Clock Speed
9 x 266Mhz, 1066Mhz, DDR2 533 RAM = 2.4Ghz <== Stock Speeds
9 x 333Mhz, 1333Mhz, DDR2 667 RAM = 3.0Ghz <== Good OC
9 x 400Mhz, 1600Mhz, DDR2 800 RAM = 3.6Ghz <== Excellent OC, About the Max