A few things:
1. Applecare warranty. If you break it, they fix it for a $50 deductible. If you break it once, the warranty pays for itself.
2. If you don't get the Applecare warranty, and you break it anyway, make sure to take it back to AAPL to get it fixed. Don't do the fly-by-night $100 cheaper than apple wefixit4u places.
3. There are great deals on refurbs (look in the Apple store online), ESPECIALLY if you don't need the current gen model. Find out whatever feature is different between the one they're making now and the previous model. If you can live without it, save yourself $250 and buy the older one. I can get a refurb with a warranty and everything for about half of what I paid for a brand new one 11 months ago.
4. 16GB isn't nearly enough. I can't say this enough. 16GB ISN'T ENOUGH. My iPad just got wiped a few weeks ago. It's currently sitting at 16.1GB USED. There's not really anything on it. Before it got wiped, I was up to 34GB. I don't understand why they sell the 16GB model. Seems like a ripoff.
5. $339 is the current price in the Apple store for a 16GB refurb iPad Air with wifi. That's probably the same thing you're looking at from Staples.
Edit: Nevermind what I said about the applecare warranty if you're set on spending <$400. If you break it, just buy another one.