Most coolers that fall in this category are similar in design (stacked fins with 6-8 heatpipes). The most conclusive way is to find reviews of HSF roundups. If you want the best cooling possible for overclocking get something like the Sonic Tower and whack in 3 high cfm 120mm fans. Problem is u can easily spend double the money for 2c difference so price to performace is huge.
The processor in my sig consumes 19w more than the e6300 and my HSF does a fab job, so when i get my conroe things will only get cooler
Also looking good at the price is this one - Titan Tower TTC-NK34TZ Heatpipe Cooling Fan (Socket 775)