Add Rotel, soups, onion and cream cheese and cook over low heat until cheese has melted.
Add chicken to the mix and chili powder to taste.
Spray 9 by 13 pan with nonstick spray. Coarsely crush the Doritos and layer 1/3 of them in the bottom of the pan. Layer half of the chicken mixture over the Doritos layer.
Sprinkle with half of the shredded cheese over chicken.
Spread another 1/3 of the Doritos over this layer and the rest of the chicken mixture. Finish with the rest of the Doritos and then top with remaining cheese.
Bake @ 350 degree oven for 30-35 min or until hot and bubbly and the cheese has just started to brown.