In a small bowl, mix graham cracker crumbs and Splenda. Add melted margarine and mix thoroughly. Place crumb mixture in bottom only of 10 inch non-stick spring form pan and pack down firmly. Place in refrigerator for 1 hour.
Preheat oven to 375 degrees.
In a medium bowl, beat cream cheese until creamy. Add Splenda, vanilla and eggs one at a time and beat until smooth and no lumps. Fold in 2 cups of sour cream. Pour filling into spring form pan on top of graham cracker crust.
Bake with a water bath in oven for 45 minutes or until outside edges are puffed and center is still a little jiggly. Then take cheesecake out of oven and let cool on counter top for 1 hour. Then place cheesecake in refrigerator and allow 6 - 8 hours to cool before eating.