Depends on what your sample is capable of really.
For mine I could do 4.0GHz @ 1.076V. It passed a few tests but I think it BSOD after 5ish hours in a stress test, so I'd have to tweak it some more.
Have been running stock since those tests so I can't give you a precise answer of my chip at 4.0GHz. Just that I should need a little over 1.076V ^_^ I also have no idea whatsoever of where such a result would place the chip, bad, average or above average results.