I was talking to a guy at Gap a couple of weeks ago using the 30% off voucher and he said Amex have Gap offers sometimes, too. I checked and they don't have any currently, but do have some nice discounts - you can find them here. The my-wardrobe code is for 20% off and hq hair is 15%. To get them, you need to go through their links and use your Amex card and a code if they provide one.