Heat oven to 350°F.
In large bowl, combine potatoes, butter, salt, pepper and garlic powder; mix well.
In separate large bowl, combine cheese, SPAM® Classic, soup, sour cream, milk, onion and chiles; mix well. Stir into potato mixture. Pour into 2-quart baking dish. Sprinkle with crushed chips.
Bake casserole 45 to 60 minutes or until heated thoroughly.