Thats what they do do.
The Extreme models are unlocked, which cost triple or even quadrouple the money.
EDIT:
I still can't overclock my brothers Asus Striker Extreme. It may be the BIOS, but setting to manual overclock doesn't allow me to change the FSB. Only the Multiplier.
I don't want to resort to using the automatic Asus ones in the BIOS... they only offer 5%, 10% overclocks, etc.
Hes being a ******* though, as he hasn't thanked me yet for choosing parts, building it, setting it up. All I've heard from him has been moaning.