2.1? That thing should do 3ghz easily. Although I did have issues with the Intel TIM wearing out or something, but my 3-4 friends that also bought that processor had no such issue(all overclocked to 3ghz+ with similar settings +Stock Cooler).
I agree that his CPU can overclock mich higher than 2.1 Ghz.
However, since I've used that particular model motherboard and have overclocked several CPUs on it, it's rather weak and almost pointless to go for any significant gain and attempting do so makes the system unstable.