Hi Cat...Can you believe I have a recipe called the Indiana Creamy Peach Pie...It sounds very much like what you are looking for..and as far as the sugar in the topping goes I would bet you could substitute brown sugar if you wanted..but perhaps you might want to try her original recipe first.
This is from the PERFECT FRUIT PIES, AWARD-WINNING RECIPES FROM ACROSS AMERICA,1991. Hope this is it!!This is a Grand-Prize winning recipe by Anne Marie Scher
Indiana Creamy Peach Pie

=== CRUST ===
1 1/2 cups All-purpose flour
1/2 teaspoon Salt
1/2 cup Butter
=== FILLING ===
4 cups Sliced fresh peaches
1 cup Sugar
2 1/2 tablespoons All-purpose flour
1 Egg
1/4 teaspoon Salt
1 teaspoon Vanilla extract
1 cup Sour cream
=== TOPPING ===
1/3 cup Sugar
1/3 cup All-purpose flour
1/4 cup Butter

Preheat oven to 400 degrees.
For crust, combine flour and salt and cut in butter. Press into a 9-inch pie plate.
For filling, put peaches into a bowl. Sprinkle with 1/4 cup sugar and set aside. In another bowl, combine remaining sugar, 2 1/2 tablespoons flour, egg, salt, and vanilla. Fold in sour cream. Stir mixture into peaches. Pour into crust. Bake for 15 minutes. Reduce heat to 350 degrees and bake 20 minutes more.
Prepare topping by combining all ingredients until crumbly. After baking at 350 for 20 minutes, sprinkle topping evenly on top. Bake for 10 minutes more at 400 degrees. This recipe serves 6 to 8.