Don't forget you can buy gift certificates for Blu Nile through giftcertificates.com and earn miles and then use those to make a purchase that earns miles as well. Make sure you are aware of the fee's . Usually not worth it for small $ purchases but for large amounts it could be beneficial.
Warning...in order to qualify for the double miles bonus, you have to use a Mastercard. I suppose you can use a Mastercard to buy the gift certificate but there are typically limits on those whereas BlueNile has no such limit.
For a limited time, you can also save $100 on your diamond order over $500.* Simply place your order before 3 PM ET on December 11 and enter DIAMOND47 in the Reference Code box at checkout.
According to the terms and conditions, this will make you ineligible for miles, at least through AA eShopping.
I'm the guy that started that thread over in the AA forum. I've been thinking about this for weeks and I'm within a day or two of making the purchase.