Dice the cheese and place in a large saucepan. Mix in the 2 cans of diced chili's and tomatoes one at a time. Simmer over low-medium heat until cheese is melted and all ingredients are mixed in nicely. Stir in the garlic powder. If this seems a bit runny from the juices, you can put in a teaspoon or so of cornstarch to thicken the dip. This gets better each day it is refrigerated.