Mix sour cream and 1-1/3 cups sugar in large bowl until blended. Gently stir in Cool Whip.
Place 1 large cake layer on plate; spread with 1-1/2 cups of the Cool Whip
mixture. Repeat layers twice. Top with 1 small cake layer, centering it over the large stacked cake layers. Spread top of small cake with half of the remaining Cool Whip
mixture. Repeat layers. Garnish with strawberries; sprinkle with remaining icing sugar.