Your are not going to overclock well at all on air with a quad with any stepping (Compared to a E6600). I would say you would get 3GHZ tops because of temp issues. Don't count on it. You might only get 2.8... Not sure how well your air cooler performs, i've never seen charts of it, or seen anyone here using it.
Now if you went CUSTOM top-end water, then you could get 3.0+ easily.
Now if you went CUSTOM top-end water, then you could get 3.0+ easily.