You can't use 2 CCs on DL's website. But you can use a DL gift card and a CC to cover the rest. So you could try buying a gift card for the amount over $1200. Then apply that gift card to the transaction, and pay for the rest with the CC you get on the spot through the offer. I don't know if using a gift card will invalidate the offer you're getting, but it can't hurt to try.