Preheat the oven to 375 degrees. Coat a 9"x13" pan with cooking spray.
In a medium bowl, mix together the monterey jack and cheddar cheeses.
In a large bowl, mix together the chicken, 1/2 of the cheese, green chilies, garlic powder, cumin, onion powder and salt and pepper to taste.
Stack the tortillas on a plate and wrap with a damp paper towel. Microwave for 1 minute until tortillas are warm and pliable.
Lay one of the tortillas on a flat surface and spread approximately 2 teaspoons of sour cream down the center of each tortilla. Add approximately 1/3 cup of the chicken mixture, then tightly roll up the tortilla and place it seam side down in the pan.
Repeat the process with the remaining tortillas.
Pour the enchilada sauce over the top of the pan, the top the enchiladas with the remaining cheese.
Bake for 20 minutes or until cheese is melted. Serve, topped with chopped cilantro and tomatoes if desired.