In medium bowl, whisk together flour, baking powder and salt.
For cake, beat brown sugar and butter with electric mixer in large bowl until light and fluffy. Add eggs, 1 at a time, beating well after each addition. Add vanilla; mix well. Add flour mixture alternately with sour cream in 3 additions. Spread mixture into prepared pan.
Bake 34 to 38 minutes or until a toothpick inserted into the center of the cake comes out clean. Cool completely in pan on cooling grid.
To prepare peaches, preheat grill or grill pan to medium-high heat. Grill peaches 3 to 4 minutes or until grill marks start to show. Let cool completely. Slice peaches 1/4 in. thick.
To prepare icing , beat cream cheese, sour cream, and vanilla with electric mixer in large bowl until smooth. Add confectioners? sugar, 1 cup at a time, beating until smooth. Beat in 3/4 cup toasted pecans. Spread icing on top of cooled cake. Just before serving, top with peaches and sprinkle with remaining 1/4 cup pecans.