I would suggest Sound Horizon, they're like my favorite band when it comes to neoclassical/opera/rock stuff, especially that they also carry stories/meaningful messages in each of their albums, making them more interesting.
Here are some of my favorites from them:
Yoiyami no Uta (the first one):
http://mp3juices.com/search/Sound-Ho...Yoiyami-no-Uta
Hikari to Yami no Douwa (also the first one):
http://mp3juices.com/search/Sound-Ho...-Yami-No-Douwa
Arasoi no Keifu:
http://mp3.zing.vn/bai-hat/Arasoi-no.../ZWZAEUDA.html
(sorry that i couldn't find youtube videos of 'em, their label seem to delete everything so I hope the links work for you ^^; )