Cook the spaghetti as directed on the box, careful not to overcook.
In a large skillet, combine cream cheese and 2 cups cheddar cheese over medium heat. Stir continuously until mixture begins to melt.
Gradually add the chicken broth until the mixture is creamy. (You want it to be creamy, not soupy, this may not require ALL of the broth).
Add in the green peppers, onion, pimentos, and spices.
Combine the noodles, sauce, and chicken in a large casserole dish. (If the mixture seems to dry at this stage, add in a small amount of the remaining broth as needed.)
Top with remaining cheese and bake at 350 degrees for 45 minutes or until bubbly.