I partly agree with all you've said, but maybe I wasn't very clear as to what point I was trying to make.(After all, writing and communicating is something I've had to work on, especially since I've gotten envolved in music forums)
I disagree however with your definition of progressive metal. Using Deaths progression of albums sequencially, you define prog metal with the wrong form of the word progress. Historically, as I stated in my earlier post, prog began as a style of music that combined classical music's sense of space and monumental scope with rock's raw power and energy, along with what Yngvai X said about incorporating many different styles, thus creating new and interesting music, I.E. prog rock. The genre was never based solely on progression from one album to the next, but in each song, work, what have you, begginning to finish. This is why 'prog metal' is in reality such a broad genre, but most refer to it in the form of a certain sound, like that of Evergrey, Dreamscape, earlier Dream Theater, and so on. But because Symphony X incorporates the same attributes as those first considered 'prog' in the 70's, they do falll under the wide scope that is prog metal. With prog rock, prog metal, and the easily understood(to those who are familiar) metal defined, you can now classify the many, and reasonably newly created sub-genre's. It is complicated, unless you truly understand how things progressed from the start, from the fathers of prog. I honestly don't care if anyone wants to keep their opinion, but that doesn't mean that I won't be progressive enough to share mine, along with a little history supporting it.
\m/