Preheat oven to 375 F. In a bowl combine crushed graham crackers and 6 tablespoons sugar. Add melted butter and stir with a fork until all crumbs are moistened. Take out 1 1/2 cup crumbs and set aside for topping.
Press the remaining crumbs into the bottom of a 13×9 inch baking dish and bake for 8 minutes. Set aside to cool.
In a sauce pan combine water, 1 cup sugar and cornstarch, stir well and bring to a boil. Add the package of peach Jell-O and stir to dissolve. Remove the mixture from heat and allow to cool completely, then add diced peaches, stir and pour over cooled crust. Place in the fridge until set (about 4 hours).
Cream together powdered sugar, cream cheese and vanilla. Fold in cool whip and spread over the top of peach filling. Place in the fridge to set and top with the 1 1/2 cup reserved graham cracker crumb mixture before serving.