Nancy B - I too have a similar recipe for streusel coffee cake. I think you will like the cake better in mine - it jazes up the box cake. I like your 9x13 pan size. This recipe gives you two 9" round cakes (one to stay home and one to take to a friend!)
1 1/2 cups graham cracker crumbs

1 cup chopped nuts

3/4 cup brown sugar

1 1/2 tsp. cinnamon

3/4 cup melted butter
1 pkg. yellow cake mix

1 cup sour cream

1/4 cup water

3 eggs
Preheat oven to 350. Grease and flour two 9" cake pans. Combine first five ingredients in a large bowl and set aside.
In mixing bowl, combine cake mix and remaining ingredients. Beat at low speed until moistened; beat 2 minutes at medium speed of Kitchen Aid mixer, high speed of hand held. Pour 1 1/4 cups batter into each pan. Sprinkle with 3/4 cup streusel mix. Divide remaining batter between pans and top with remaining streusel. Bake 350 for 35-40 minutes, or until wooden pick comes out clean. Cool in pan 15 minutes. Then remove to racks, cooling stresuel side up. Serve warm or cold.
Janet in NJ

jcm119@aol.com