I guess if you have to use tech death, Lykathea Aflame is probably a good choice. If many people who like metal can't get into Gorguts or Crimson Massacre, then how is someone not familiar with metal going to get what's going on? It seems doubtful to me. Lykathea Aflame is at least much more melodic and accessible for a first time listener.
I Am The Black Wizards would probably be a good choice, as it is widely held as one of the best composed metal songs, and it has some relation to classical structure.