Apple iPhone 5S: Where to Buy It Sept. 20 and Get the Best Deal

AT&T customers who don't want to take chances, can get their orders in a little early. While AT&T retail stores will open at 8 a.m., the carrier will begin selling the iPhone 5S online, starting at 3:01 a.m. ET.

Still, it's unclear how quickly those buyers will receive their phones. When I asked an AT&T spokesperson whether a phone ordered at 3:30 a.m. Friday would arrive on Saturday, or just eventually, I was told that "online orders are fulfilled on a first-come, first-served basis."

The Best Deal for the iPhone 5S

If you're contract-free and ready to buy, the 16GB iPhone 5S will retail for $199 with a new two-year contract and the 32GB for $399 with a contract.

Verizon, AT&T and T-Mobile now all offer monthly device financing, and it's expected that on the morning of Sept. 20, Sprint will get on board, as well.

Which carrier offers the best deal depends on what's most important to you: not having a contract, paying a low up-front cost or getting the best deal over a two-year stretch.

Laptop put together a good chart breaking down the payments (sans any Sprint announcement, off course). Bottom line: The 16GB iPhone 5S, as things stand, are cheapest month-to-month on Sprint, where a 1GB Unlimited My Way data plan will run you $80 a month—though for $83 a month, you can get a 2.5GB T-Mobile plan.

Over a two-year span, the best deal is again with Sprint and the 1GB plan, which totals $2,055. The next best is again the T-Mobile 2.5GB plan, totaling $2,100.

If it all seems like too much trouble, you can find comfort in purchasing what Apple calls the "most forward-thinking smartphone in the world."

Or, you can take HTC up on its offer to pay up $150 or more for old iPhones and other smartphones, when you purchase an HTC One. And, of course, there's always the lower-end iPhone 5C. According to reports from carriers in the U.K., preorder demand has been underwhelming. You're almost guaranteed your color of choice.  

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