You can't raise the multiplier on a Q6600, it's locked. Overclocking is limited to raising the FSB.
The motherboard natively supports an FSB of 1333Mhz, so setting this speed would not be overclocking the motherboard at all, this would cause zero strain on your motherboard, it's designed for it. An FSB of 1333 would give you a CPU speed of 3.0Ghz.