Place potatoes in a Dutch oven or large kettle; cover with water and bring to a boil. Reduce heat; cover and cook for 20-25 minutes or until potatoes are tender.
Drain potatoes and place in a bowl; mash.
Add sour cream, cream cheese, 4 tablespoons butter, onion and salt; stir until smooth and the cream cheese and butter are melted.
Spread in a greased 13-in. x 9-in. baking dish.
Melt the remaining butter; drizzle over the potatoes.
Sprinkle with paprika. Refrigerate or bake immediately, covered, at 350° for 40 minutes; uncover and bake 20 minutes longer. If potatoes are made ahead and refrigerated, let stand at room temperature for 30 minutes before baking.