Preheat oven to 350 degrees F. Coarsely chop 20 of the wafers; set aside for later use. Finely crush remaining 30 wafers; place in medium bowl. Add flour, baking powder, and baking soda; mix well. Set aside. Beat 1/4 cup butter and sugar in large bowl with electric mixer on medium speed until light and fluffy. Blend in vanilla. Add eggs, 1 at a time, beating until well blended after each addition. Add flour mixture alternately with the sour cream, beating well after each addition.

Microwave 2 tablespoons butter in medium microwaveable bowl on HIGH 30 seconds or until melted. Add the reserved chopped wafers along with the pecans and cinnamon; mix well. Spoon half of the cake batter into greased 12-cup fluted tube pan or 10-inch tube pan; top with half of the pecan mixture. Repeat layers.

Bake 45 to 55 minutes or until toothpick inserted near center comes out clean. Cool 10 minutes in pan on wire rack. Loosen cake from side of pan with spatula or knife. Invert cake onto wire rack; gently remove pan. Cool completely. Invert cake onto serving platter, streusel-side up, to serve.

Special Extra: To add a simple glaze, mix 1-1/2 cups powdered sugar and 2 tablespoons milk until well blended. Drizzle over cooled cake. Let stand until set.