Why would you overclock really? I see no point really - I view overclocking as a last resort measure to bide time until the next CPU upgrade.
I see reviews of people overclocking this CPU by nearly 1 GHZ and all they get it like 10% more juice out of it and mostly where it does not matter anyway (like going from 48 FPS to 52 or from 20 FPS to 22), what's the point really?
And besides that, if you are buying such a heavy rig, why not fork over a bit more for I7 CPU? Why not really? Hyper-Threading HAS it's uses, for example if you game AND have background apps running and lately latest titles popping do manage to make use of HT even if by a bit.