I'm glad to see some Classical music mentioned. It can be absolutely exquisite on psychedelics -- even if it's normally not your thing.
For me, Scarlatti sonatas played on harpsichord can get super-intense. In particular, because the harpsichord is such a foreign instrument to us today, and because it makes all sorts of very weird mechanical noises, the effect is somewhat "electronic" and other-worldly -- which I know a lot of you guys like. And Scarlatti is happy, happy, happy. It's all Mediterranean sunshine -- no bad moods here. I've found Scarlatti to be very reliable in keeping things feeling good and on a positive plane.
One example of exactly 555 (there's really no running out):
http://www.youtube.com/watch?v=3vpG1PgFF34