Spread 3 cups dried stuffing on bottom of greased 13x9-inch baking pan; set aside.
Stir together chicken, broccoli, chicken soup, mushroom soup and pimiento in large bowl. Spoon over stuffing; sprinkle with cheese. Combine all remaining ingredients except 3 cups dried stuffing and butter in medium bowl. Pour over chicken mixture. Cover; refrigerate 8 hours or overnight.
Heat oven to 350°F. Sprinkle with remaining dried stuffing; drizzle with butter. Bake for 1 to 1 1/2 hours or until set and heated through.