Viperware, that was an excellent, spot-on analysis. While my tastes don't mirror yours, I know the feeling of moving on to harder stuff to extract those extra chemicals from the brain.

You can look at porn like you look at music. Some people will just be happy with the shit on the radio (Vivid, Wicked). Others will branch out, latch on to a specific genre or genres, artists, styles that best suit them and that "expands" their enjoyment. Porn is just visual music.