Prepare cake batter according to package directions. Pour into 3 greased and floured 8-inch round cakepans.
Bake at 325° for 20 to 25 minutes or until a wooden pick inserted in center comes out clean. Cool in pans on wire racks 10 minutes. Remove from pans, and cool completely on wire racks.
Beat cream cheese, powdered sugar, and granulated sugar at medium speed with an electric mixer until mixture is creamy.
Chop 8 candy bars finely. Fold cream cheese mixture and chopped candy into whipped topping.
Spread icing between layers and on top and sides of cake. Chop remaining 2 candy bars. Sprinkle half of chopped candy bars over cake. Press remaining chopped candy along bottom edge of cake.
Note: For testing purposes only, we used Duncan Hines Swiss Chocolate Cake Mix and Hershey's Milk Chocolate Bars with Almonds.