All these on-line stores operate on a very close margin, so if you see an item where a price is consistant among several stores (like
B&H, buydig.com, etc{the good ones}) and some other stores where prices are 5-10 % less, you can assume the 5-10% ones are cutting you short somewhere and you will be right.
One caveat about reseller ratings is that some time back I bought cameras from Butterfly Camera and also US1 Camera(also known as US1 Photo) which both had reseller ratings of 9.7 or higher with more than 2000 reviews. Neither of them supplied what their website said they would (and not what Canon called for), returning was not an option without restocking fees.