In a large mixing bowl, beat cream cheese, sour cream, garlic powder and pepper with an electric mixer until combined. Add 3/4 cup of the Parmesan, the Monterey Jack and Swiss cheeses. Beat until combined. Stir in chopped spinach, artichokes and sweet pepper. Transfer mixture to a 2-quart oval or an 11x7x1 1/2-inch baking dish. Sprinkle with the remaining 1/4 cup Parmesan cheese.