Preheat your oven to 325°F (163°C). Combine 1 1/2 cups of crushed graham crackers, 6 tablespoons melted unsalted butter, and 2 tablespoons granulated sugar. Press the mixture into the bottom of a 9-inch springform pan. Bake for 8 minutes, then cool.

In a large bowl, beat 24 ounces of softened cream cheese until smooth. Add 3/4 cup granulated sugar and beat until creamy. Blend in 1 cup pumpkin puree, 3 eggs one at a time, 1/4 cup sour cream, 1 teaspoon vanilla extract, 1 1/2 teaspoons pumpkin pie spice, and 1/4 teaspoon salt. Pour the filling over the cooled crust.

In a separate bowl, mix 1/2 cup all-purpose flour, 1/2 cup brown sugar, 1/2 teaspoon pumpkin pie spice, and a pinch of salt. Cut in 4 tablespoons cold unsalted butter until crumbly. Sprinkle evenly over the cheesecake filling.

Bake the cheesecake at 325°F for 55-65 minutes or until the center is just set. Cool completely at room temperature, then refrigerate for at least 4 hours or overnight.