PREHEAT oven to 350°F. Beat butter, 1/2 cup of the sugar and 1/2 tsp. of the vanilla in large bowl with electric mixer on medium speed until light and fluffy. Gradually add flour, beating on low speed after each addition until well blended. Press firmly onto bottom of 13x9-inch baking pan. Bake 20 to 23 min. or until lightly browned.
BEAT cream cheese, remaining 1/2 cup sugar and remaining 1/2 tsp. vanilla in large bowl with electric mixer on medium speed until well blended. Add eggs; mix well. Stir in toffee bits. Pour over crust. Drop teaspoonfuls of the caramel topping evenly over cream cheese mixture. Cut through batter several times with knife for marble effect.
BAKE 30 min. or until center is almost set. Cool completely. Refrigerate several hours or until chilled. Cut into 32 bars to serve. Store leftover bars in tightly covered container in refrigerator.