These guys remind me of BWay Photo, Digital Liquidators, A&M photo, and those other grey market scammers.
Be very cautious.
I'd first recommend B&H Photo, then J&R electronics, they both have the best reputation.
Go to Bizrate.com and check out their customer reviews/ratings of the various merchants, you'll see there and in other customer ratings, like Cnet's ratings if they've got a good track history.
Aside from the obvious B&H Photo and J&R electronics, I've been told that New Egg and BuyDig are reliable sellers. You'll have to check them out for yourself though.
Hope that helps...
Happy Hunting