Preheat oven to 350 degrees F. Grease and flour two 9-inch round baking pans. Set aside.
In a large bowl, combine cake mix, 1 cup pumpkin, milk, eggs, oil and 1 teaspoon of pumpkin pie spice. Beat on low speed for 30 seconds, then beat on medium speed for 1 minute. Divide and pour the cake batter evenly among the two baking pans.
Bake for 25 to 28 minutes or until a toothpick inserted near center comes out clean. Cool cakes for 10 minutes before removing from the pans to wire racks. Cool completely.
In a large bowl, beat the cream cheese until light and fluffy. Add the powdered sugar, remaining pumpkin puree and pumpkin pie spice. Beat mixture until very smooth. Fold in the cool whip.
Cut each cake horizontally to create two layers. You will have four layers total between the two cakes.Place one layer of cake onto a large serving plate. Spread 1/4 of the filling evenly over the top. Repeat layers 3 more times, ending with the filling on the very top. Sprinkle the toffee bits all over the top and then drizzle with caramel sauce. Slice, serve and enjoy!Store leftover cake in the fridge for up to 5 days.