Mastercard and Amazon have a promotion up (today only?) where you get $10 off a $100 purchase + a voucher for a future $10 off $50 purchase. Only requirement is to make your purchase using a Mastercard.
BUT: you also get a $20 Giftcard when you spend $200 online by applying for this promotion:
So if you buy $200 headphones, they end up being only $160.