The E6700 is the same thing as a E6600 just clocked 266mhz faster and running a 10x multiplier instead of 9x. It has the same Cache, FSB rating etc. The thing is when you start overclocking the E6600 can go just as high as a E6700 can. So its a waste of money unless you plan on running it at factory settings.
Example Intel has a quota to meet. Say they need 10,000 E6600 processors for a shipment. Problem is they only have 3,000. Guess what 7,000 E6700's just became E6600's.