Need recomendations for kitten food

Our kitten is about 6 months old. She has been eating Purina Kitten Chow and appears to be doing well on it, growing, active, firm stool, etc, but I am wondering about the amount of food and water coming out of the cat. Since I am cleaning the litter box daily I see what she produces and it seems excessive for a kitty her size. I thought about getting Iams or Science Diet when this bag is empty in a few more days. Those brands will cost more but I wonder if less of a better quality food would produce less results in the litter box while still meeting her nutritional needs. Somebody out there knows.