Purchase a $400 Crown Gift card and receive $100 additional value. Offer is strictly limited and valid for purchases made from 14 November – 24 December 2016. Offer is subject to availability at time of purchase, one transaction per purchase. Offer is only valid with the purchase of a $400 gift card denomination. One gift card is issued. Offer is strictly limited and only available via Crown Gifts online. Offer cannot be used in conjunction with any other offer via Crown Melbourne, Crown Perth or Crown Gifts. Please refer to crowngifts.com.au for further terms and conditions on purchases via Crown Gifts
As mentioned by feihong, multiple Amex cards can be used if you purchase at the counter.
pretty sure this is a dupe