Preheat oven to 350°. Grease and flour a 9 x 13-inch pan. Prepare cake mix according to package directions. Pour half of the batter into the prepared pan, reserving the rest. Bake 20 minutes. Melt caramels. Add milk and margarine; stir to blend. Pour caramel mixture over the baked cake. Sprinkle with peanuts and chocolate chips. Spoon the reserved cake batter over all. Reduce oven to 250° and bake cake for 20 minutes. Return oven temperature to 350° and bake an additional 10 to 15 minutes.