If you want top-performers, you can go with Prolimatech Megahalems, Thermalright Venomous-X or Noctua NH-D14.
If you're looking for the best bang for the buck, you can take a look at Scythe Mugen or Scythe Ninja.
I think he is saying so because WoW at certain points prefers more MHz over more cores. Anyway, I doubt that a CoreDuo outperforms an i7 in places like 25m Raids.