e520 cpu upgrade

​I'm in the process of upgrading the processor in my e520 currently running a Pentium D 820. I have read many posts on the topic but haven't decided between Q/E6700 or Q/E6600. My question is whether my original stock (huge) heatsink and fan with be sufficient. Although it may not be correct, I am assuming that operating wattage may indicate heat produced. My current processor is 95Watt, the E 6600/6700 are 65Watt and the Q 6600/6700 are 105Watt. If my assumption about Wattage indicating heat produced, the E series should present no problem for current cooling but the Q series might be a stretch. I would appreciate comment from anyone having real knowledge on this as I would rather not depend on my assumptions. Thanks!​