Preheat the oven to 350 degrees. Mix the cake mix, oats, butter and 1 egg. Reserve 2 cups of the mixture. Press the remaining mixture into the bottom of a 9x13-inch cake pan. Blend the icing, cream cheese, sour cream, and remaining 2 eggs and pour over the top. Sprinkle the remaining 2 cups of crumb mix over the top and bake for 45-55 minutes. Cool bars to room temperature and then store in the refrigerator. *Optional: sprinkle with powdered sugar before serving, if desired.