Beat reserved 1 cup cake mix, reserved 1 cup cream cheese mixture and remaining 1/2 cup whipping cream in same bowl on low speed until smooth. Drop chocolate cream cheese mixture by spoonfuls over cream cheese mixture in pan. Cut chocolate mixture through plain mixture with knife in S-shaped curves in one continuous motion. Turn pan 1/4 turn, and repeat for marbled design. Tap bottom of pan sharply on counter to level cream cheese mixtures.