Dichotomous Parallels in the "House of Wax"

The horror movie (if I may even term it that) which we saw on Tuesday was simply appalling. "House of Wax" was extremely disturbing (Poor Rachel and Nicola had to step outside after viewing a particularly gory scene, and stayed out till the end of the movie, waiting for us). The scenes of killing, mutilation, and dismemberment were extremely graphic, and spine-chillingly real. So real in fact, that it became almost satirical of the horror movie genre. If there was one thing that the movie was worth praising, it did manage to weave in a certain amount of philosophy and plot amongst the slaying. The concept of the "Doppelganger" (literally from the German word, "double") was used by the director in this story to show the dichotomous contrast of the two pairs of siblings. Both pairs were twins - one pair comprising a brother and sister who looked perfectly normal (even somewhat attractive), contrasted to the other pair comprising a pair of Siamese twins separated at birth. The twins in the story were used to signify the extremes of human behaviour. On one pole were the 'normal' kids who were out simply to have some fun, average teenagers who probably did decently at school. And yet on the other pole, the twins who inhabited the quaint, rustic town in the middle of the wilderness. To cut a long story (and possibly, a thesis!) short...I'd say that what we are faced with is a Jekyll-Hyde scenario - only that in this case, it comes in double servings.
Yes, the movie IS extremely disturbing, but I usually try to see behind the facade of Hollywood lights and screams to understand the script and/or storyline which is the (Creative) scriptwriter's way of speaking to the audience.