Based on my experience with Golden Sound DH Cones. Two cones in the front will increase the width of the sweet spot. One cone in the front will decrease the width of the sweet spot, however, increase the depth of the sound stage.
Generally, I like one cone in the front pointy side up and two cones in the back pointy side down.
Generally, I like one cone in the front pointy side up and two cones in the back pointy side down.