Actually, in terms of their vision and scope, I'd say Ulver. Not quite what you mean, I know, but 'Themes.." got me so excited because I felt that finally, a band was taking something as serious as, say, composing a symphony.
Anyway, some more serious stuff:
Nightwish (and not just because they have opera vocals)
Arcturus (last 2 albums (not counting the remix one))
Tristania have a choral thing happening here and there.
Within Temptation, their last album (Mother Earth) has a really full orchestral score, I think it's all synthesised, but it sounds really good (they must be rich to afford good synthesisers)
[edit] and Diabolical Masquerade- Death's Design. Movie soundtrack, it's very cool.
And In The Woods use a string 4tet on "Omnio", which is such a great album I need to mention it, though it's not really 'Classically influenced"
And Bolt Thrower. Don't forget Bolt Thrower.....
