Preheat oven to 350 degrees. In a large bowl combine dry cake mix, pumpkin, brown sugar, oil, eggs, nuts, and pumpkin pie spice. Blend at low speed until completely moistened, about 1 minute. Beat 2 minutes at medium speed. Spread batter in a greased and floured 13x9x2" pan. In a medium bowl combine the sugar, flour, softened butter, and cinnamon with a fork or pastry blender. (Mixture will be crumbly.) Sprinkle evenly over batter. Bake at 350 degrees for 40-45 minutes, until center springs back when touched lightly.