I guess it depends on what you are looking for, lowest price/best potential (aboved mentioned 2160) or if your talking lowest price/highest clocks (E8400 can achieve 4.0 or better)
Personally I would go with a lower priced cpu, 3GHz+ is very impressive on a 130$ or less cpu. Im completely satisfied with my E4300 and I spent 179$ on it when it first came out, now its like 100-110. But Im still happy I got it when I did.