I have found myself a student of feline nutrition lately and read your post with interest. I am glad to see someone else actually READS the ingredients on the bags and cans! I was beginning to think I was a freak! *smile*
From what I can gather from the little bit of research I have been able to do on the topic of feline nutrition (you are right, with the exception of individual pet food companies web sites which only promote THEIR products, there isn't much out there) I have learned that cats seem to need twice as much protein as dogs. Dry cat foods are thought to be a good source of protein, but since many have a high concentration of some minerals (known collectively as ash), they can also contribute to Feline Urinary Syndrome (FUS). Look for low ash foods (magnesium no more than .08-.10% of content, and a calcium to phosphorus ration of 1.2:1). Avoid fish-based foods, especially tuna because it is high in ash and can lead to a Vitamin E deficiency in cats.
Other factors including age and general condition determine your pet's nutritional requirements. Diets should be chosen to meet specific needs and maintain ideal weight. An animal of normal weight has ribs that, while not easily seen, can be felt without an upper layer of fat. Obesity is the most common nutritional disease in dogs and cats, prevails in older animals, and results in part from over-consumption of appealing commercial foods.
Younger cats need to be fed more often than older ones, and meal sizes and frequency must be adjusted as the animal grows. Adult cats should be fed two separate meals each day.
Hope this helps you.