Iams used to be a very good food, however it has gone downhill a bit.
I understand that feeding a $60 bags of food is hard. There is a really nice food that is not much more than Iams and is good. Called Natures Recipe, it is sold at Petco and Petsmart that I know of, maybe more places.
No corn, wheat or soy, a good natural type of food and it usually sells for around $35 a bag, which has to be close to Iams. You won't feed alot and stools are small and well formed.