Yeah, and Bach as well.
The Prelude is from Verdi, the choir thing in Lacrymosa is from Mozart's Requiem, and the kick-ass guitar+harpsichord thing in A Fool's Paradise is taken from a Harpsichord concerto by Bach (which is pretty awesome as well). I could have missed a couple of other things, but those are the most obvious ones.
Do they give mention in the credits of this, like Savatage did with a few pieces. I cant really read CD credits anymore, unless I hunt down my glasses.
I will maintain that some long hairs have written equal and/or better music than the wigs