In a mixing bowl, beat cake mix, peanut butter and brown sugar on low speed until crumbly. Set aside 1/2 cup. Add water, eggs and oil to remaning crumb mixture; blend on low until moistened. Beat on high for 2 minutes. Stir in 1/4 cup each chocolate and peanut butter chips. Pour into a greased 13in x 9in x 2in baking pan. Combine peanuts, reserved crumb mixture and the remaining chips; sprinkle over batter. Bake at 350 degrees for 40-45 minutes or until a toothpick inserted near the center comes out clean. Cool completely. Yield: 12-16 servings.