Hi, I am so glad to hear that your babies are now doing better.. that is great news.
As for the cat appeal of the various brands - what one loves, another may reject. Its a bit of a trial and error, I'm afraid... as there is no 'one" that can be said is best for 'all' cats.
The highest rated, super-premium food is of little use if your cats wont eat it.
I personally like Go Natural, Wellness and Felidae.
The amounts to feed would vary, I like free freedng of the dry, and you could experiment with the wet food as to how much to put down.
I dont know how old Hunter is.. but dont think it would hurt him to stay on the kitten for a few extra months... but not much past that.
You are right on the mark in wanting to offer the best, most nutritious food that you can afford, and that your cats do well on.
Through research and a bit of experimenting with your kittens.. you can find just the right combo - and that will be the best food for you..
Here is a link of cat food comparisons that may be of help. The foods listed are widely thought to among the best in a commercial food..any of these would be a good choice.
Good luck with this!