the thing is, most MOST prog is about developing ideas or whatever you think it is. prog has two major divisions:
a) the bands that take established ideas and combine or explore them (aka mixing classical music with rock: ELP)
b) the bands that are experimental with the boundaries of music as a whole and MAYBE JUST MAYBE create something never heard before (this is bands like Sonic Youth (ew...) incorporating noise as a musical device).
Not to jump on the whole genre bandwagon or whatever, but that definition kinda includes everyone from Little Richard to Black Flag to Public Enemy! I mean, I see where you're coming from, but it's kinda like how the word 'pop' technically includes every sort of music while in general people have a tendancy to associate it with a particular sound... You can argue about the original meaning of the word or whatever, but by this stage it's so strongly associated with a particular sound that what it originally meant is kind of irrelevent.
Anyway, I really don't like symphonic prog... I dunno, to me it just sounds like a kind of half-assed mixture of rock, jazz, and classical, which doesn't have any of the features that make those genres so appealing in the first place: it's rock without the raw power and emotional directness, it's jazz without the sense of fun and spontaneity, it's classical with the subtlety and nuance stripped out. Mix all those things together, and you end up with stuff like this:
http://www.youtube.com/watch?v=N0FuFfcCZiE... Bombastic, po-faced, cheesy as hell, and just overall hilariously, wince-inducingly awful. I mean, yeah, a link of ELP doing a classical cover might be kind of a cheap shot, but I've listened to the other bands you've mentioned and for the most part they're not much better! The problem isn't that they're
too boundary-breaking and experimental, the problem is that they're not nearly experimental
enough: they just sound like cheesy, bland, neutered rock music, with some awkward classical/jazz influences shoehorned in. You can add in some crazy tempo changes and harmonium solos or whatever, but really the whole point of experimenting in music in the first place is so that you get a fresh, exciting new sound, and most of this stuff just comes off as an awkward exercise in self-indulgence.
So yeah... This is just my own personal opinion and stuff, but I just feel like symphonic prog is pretty uninteresting as a genre, since it feels more like an attempt to gentrify rock music (heh, who needs 'sex' or 'raw power' when you've got lengthy instrumentals and sci-fi concept albums, amirite?) and to try to make some misguided bid for 'artistic credibility' by jamming in half-assed classical influences rather than a genuine, natural attempt to make a great new sound. So yeah, massive run-on sentences aside, I'm not a big fan.