I think the best is brewmaster's warehouse. Haven't had the chance to shop there yet, but I am going in a few days. His selection is great, and he has some great discounts for using his brew builder tool. You can place an order for a recipe, and save it for later. They are also very prompt in responding to questions.
Brewmasters Warehouse off Roswell Rd. just east of the 120 loop has been a good trip. I got a reasonable price on some basic items - good for starters. It looks like they have just moved into their new location, so they might still be in transition but they helped me with everything I needed.
I'll have to check out BMW while I am in town. I've been to the Beer Necessities store in Alpharetta and is the biggest homebrew store I've ever been in.
Why not check out BMW online right now?! Ed (the owner) first started off as an internet retailer (and didn't have a license to sell locally). Now he does have a storefront, but I find it's easier to order everything online and then just do an in store pickup. What's convenient about BMW is that you can save all your recipes, so it makes ordering again a snap. Ed seems a bit cheaper then Beer Necessities too. I occasionally still go out to Beer Necessities to get my CO2 filled, or if I'm desperate for something BMW is currently out of....but especially if you're going to be close to BMW, you shouldn't find a reason to need to go out to Beer Necessities (Ed is very knowledgeable about brewing if you need pointers...though honestly, I think Bob at Beer Necessities might have better AG recipes). Both shops have their own strengths, and both are doing well.