PetSmart has the 4lb bags of Authority Cat Food marked down to $5.99 though September 25th. There is also a printable coupon available that will make for a very nice deal:
Authority Cat Food 4lbs $5.99
–$5 Authority Cat Food Printable Coupon
You will also want to make sure to keep an eye out for tearpads under the cat food for two FREE 6oz cans of Authority wet cat food with any dry food purchase!