Place crumbs in mixing bowl and add quarter cup sugar and cinnamon, then stir in one third cup butter. More butter, up to 0.75 cup, may be added if needed. Butter an 20 cm springform pan on bottom and sides. Sprinkle thin layer of crumbs on bottom of pan and press down with metal 0.25-cup measure. Pat crumbs on sides and press into position with side of measuring cup. Work around sides with fingers to make crumbs of even height. Any remaining crumbs may be added to bottom crust. Bake crust at 180ºC 5 minutes. To make filling, beat eggs until light, then add half cup sugar and beat 5 minutes. Add cream cheese and 1 teaspoon each vanilla and Grand Marnier and mix well. Turn into Crumb Crust and bake at 190ºC 20 minutes. Cool 15 minutes. To make topping, blend sour cream, 6 tablespoons sugar and 1 teaspoon each vanilla and Grand Marnier well, then pour over filling and bake at 250ºC 5 minutes. Cool cake then chill overnight before serving.