Without getting too extravegant, or breaking the bank, it's nearly impossible to reach that magical 4ghz mark with any of the current C2D cpu's. My question to you is, what on earth do you need it for? I know it's sweet to have bragging rights and to push your rig to the max, but you'd be hard pressed to find a program that C2D's can't crunch with style, at any speed. Phase change might get you there, but surely you won't spend <$500 to get 36.72 more FPS in F.E.A.R., right?
