Preheat oven to 350° Grease four 7×3 inch loaf pans.
In a small bowl, stir together 1/4 cup white sugar and 1 teaspoon cinnamon. Dust pans lightly with cinnamon and sugar mixture.
In a large bowl, cream butter and 3 cups sugar. Mix in eggs, mashed bananas, sour cream, vanilla, cinnamon, and nutmeg. Mix in salt, baking soda and flour. Stir in nuts. Divide into prepared pans.
In a small bowl, mix together brown sugar, flour, and cinnamon. Cut in butter until mixture resembles coarse cornmeal. Sprinkle topping over prepared pans.
Bake in preheated oven 55-60 minutes or until a toothpick inserted into the middle comes out clean.