Thanks for your replies!
I mixed in Nutro with Iams today and he loved the new food! At first he would only eat the Nutro but i eventually got him to eat some of the Iams too cuz i didn't want him to get an upset tummy.
I would like to feed him something that is 5 or 6 stars but think all of them are really expensive...probably more than my husband wants to spend on food. I guess we'll just have to stick with Nutro.