Heat oven to 350 degrees F. Line 13x9x2-inch baking pan with foil, extending foil beyond pan sides. Prepare CRUMB CRUST.

CRUMB CRUST: Stir together 1-1/2 cups graham cracker crumbs and 3 tablespoons sugar in medium bowl; blend in 6 tablespoons melted butter or margarine, mixing well. Press mixture onto bottom of 13x9x2-inch baking pan.

Beat cream cheese, sugar and salt in large bowl until smooth. Add eggs, one at a time, beating well after each addition. Stir in vanilla. Set aside 3-1/2 cups batter; blend light cream and rum extract into remaining batter. Stir in walnuts, if desired.

Place caramel chips in medium microwave-safe bowl. Microwave at MEDIUM (50%) 1 minute; stir. If necessary, microwave at MEDIUM an additional 15 seconds at a time, stirring after each heating, until chips are melted and smooth when stirred. Gradually stir rum and nut batter into melted chips, stirring until well blended.

Alternately drop vanilla batter and caramel nut batter by heaping tablespoons onto crumb crust. With knife or small spatula swirl batters for marbled effect. (Batters will flatten and smooth as cheesecake batter bakes.)

Bake 35 to 40 minutes or until center is set and edges puff and begin to crack. Cool in pan on wire rack. Refrigerate until chilled. Using foil as handles, lift from pan. Cut into bars.