I think stock Intel heatsinks are fine if you don't plan on overclocking, i get temptures of around 30-40 degrees on computers i build with intel heatsinks underload, which is fine for a processor.
anyways ... what do you plan on using your computer for, cause the Q6600 (quad 2.4) isn't much more expensive, its like $10 more in my country (New Zealand) i donno bout yours .. but it'd definately be better at muilty tasking and 2.4ghz per core should be fine for most application