In a large mixing bowl, combine the softened cream cheese and sour cream. Use a hand mixer or a whisk to blend them together until the mixture is velvety and smooth.

Gradually fold in the shredded cheddar and Monterey Jack cheeses into the cream mixture, mixing until all ingredients are thoroughly incorporated.

Sprinkle in the garlic powder, onion powder, and optional spices. Stir everything together well to ensure even distribution of flavors.

Transfer your cheese mixture into a baking dish or slow cooker, and bake at 350°F (175°C) for about 20-30 minutes, or heat in the slow cooker until melted and bubbly.

Once bubbling and gooey, remove it from the heat and serve warm with tortilla chips, crusty bread, or fresh vegetable sticks.