Beat butter at medium speed of an electric mixer until creamy; gradually add sugar, beating well. Add egg yolks, one at a time, beating after each addition. Stir in vanilla.
Combine flour, graham cracker crumbs, soda, and salt; add to butter mixture alternately with buttermilk, beginning and ending with flour mixture. Mix at low speed after each addition until blended.
Beat egg whites at high speed until soft peaks form. Gently fold beaten egg whites into batter. Pour batter into 3 greased and floured 9" round cakepans.
Bake at 350° for 20 to 25 minutes or until a wooden pick inserted in center comes out clean. Cool in pans on wire racks 10 minutes; remove from pans, and cool completely on wire racks.
Reserve 1 1/4 cups Peanut-Coconut Frosting. Spread remaining frosting between layers. Stir 1/2 cup whole peanuts into reserved frosting. Spread on top of cake.