1. Prepare Pumpkin Batter: Preheat oven to 350°. Grease 3 (9-inch) round cake pans. Line bottoms with parchment paper, and grease and flour paper. Combine 2 cups flour and next 6 ingredients in a small bowl. Beat 1 1/2 cups granulated sugar and next 3 ingredients at medium speed with a heavy-duty electric stand mixer until blended. Add pumpkin, beating until blended. Add buttermilk, beating until blended. Gradually add flour mixture, beating at low speed just until blended after each addition. Pour batter into prepared pans.
2. Prepare Cream Cheese Batter: Beat cream cheese and next 4 ingredients at medium speed with a heavy-duty electric stand mixer until creamy. Add eggs, beating until blended. Drop Cream Cheese Batter by heaping tablespoonfuls onto pumpkin batter in pans, and gently swirl with a knife.
3. Bake at 350° for 25 minutes or until a wooden pick inserted in center comes out clean. Cool in pans on wire racks 10 minutes; remove cakes from pans to wire racks, and cool completely (about 40 minutes).
4. Meanwhile, prepare Pecan-Praline Filling: Bring 1/2 cup brown sugar and next 2 ingredients to a boil in a saucepan over medium heat, whisking constantly. Boil, whisking constantly, 1 minute or until sugar is dissolved. Whisk together half-and-half and cornstarch in a small bowl until smooth; gradually add to brown sugar mixture, whisking constantly. Return to a boil, and boil, whisking constantly, 1 minute or until thickened. Stir in pecans and 1 tsp. vanilla. Cool mixture 20 minutes.
5. Spread filling between cooled cake layers.
6. Prepare Spiced Whipped Cream: Beat heavy cream at medium speed with an electric mixer 1 minute. Add powdered sugar and next 2 ingredients, beating until soft peaks form. Spread frosting on top and sides of cake.