Beat cake mix, 1/2 of the pumpkin, milk, oil, eggs and 1 teaspoon of the pumpkin pie spice in a large bowl with mixer on medium speed until well blended.
Pour evenly into prepared pans. Bake 20-22 minutes or until toothpick inserted in center comes out clean. Cool completely on wire racks.
Beat cream cheese in small bowl with mixer on medium until creamy. Add powdered sugar, remaining pumpkin and remaining pumpkin spice; mix well. Stir in cool whip.
Remove cakes from pans. Cut each on in half. Ice between layers and the sides. Do not ice the top.
Drizzle caramel topping and cover with nuts. Slice and serve.