Actually, a lot of what you're talking about sounds like a branch of post rock headed by Canadian moguls Godspeed You Black Emperor! and Dirty Three and also Scotland's Mogwai. Not very many vocals, though, but the same churning epic melodies that usually denotes classical music.

In fact, Godspeed You Black Emperor! did Adagio for strings on their EP Slow Riot for New Kanada. So it's been done, and done well.