Preheat the oven to 350°F (175°C).
Cook spaghetti according to package instructions until al dente; drain and set aside.
In a mixing bowl, combine cream cheese and sour cream until smooth.
In a skillet, brown the ground beef; drain excess fat. Stir in marinara sauce, garlic powder, and Italian seasoning. Simmer for 5 minutes. Season with salt and pepper.
In a baking dish, layer half of the spaghetti, followed by the cream cheese mixture, then the beef sauce, and half of the mozzarella. Repeat layers.
Bake for 25-30 minutes, until bubbly and cheese is golden.