Amazon is a very reliable online vendor.
However, there is one huge potential problem. There is no indication that I can find that Amazon is an Authorized Apple Retailer. (You may want to e-mail them and ask about this, and/or write to Apple and ask, to be sure about this.) Apple's authorized retailers are required to show a banner that tells customers that they are authorized, and I don't see this on the pages where new Apple products are offered for sale.
Apple doesn't allow non-authorized vendors to sell their products. Apple products sold by non-authorized retailers are called "gray market goods." Gray market goods are technically illegal to sell. Not from a criminal aspect, but from a violation of contract standpoint. (Apple contracts with all of their authorized retailers that they will not trans-ship goods to non-authorized retailers. So, any non-authorized retailer is selling goods in violation of someone's contract with Apple. Not only is the authorized retailer in violation of contract, but inducement to violate a contract, by the non-authorized retailer, is also illegal.)
Apple can, and has been known to, refuse to give warranty service on gray market goods. It might not be worth it to you to risk this. So you may want to be absolutely sure about this before you purchase from Amazon.
___________________________________________
Randy B. Singer
Co-author of The Macintosh Bible (4th, 5th, and 6th editions)
Macintosh OS X Routine Maintenance
OS X Maintenance And Troubleshooting
___________________________________________