Sion, I believe that my mother owns some CSNY albums. I'll be sure to look into that. As for Dream Theater, I have to say, they're the type of metal band that pushed me to the more extreme corners of the (very broad) genre. They're such amazing musicians but as a group they don't do much for me. Thanks, though. I believe that a friend of mine has Operation: Mindcrime and I'll be sure to borrow that from him and also look into the others you suggested.
willravel, do you know where I can listen to legal samples of those songs? I'll check, but I doubt they have Myspaces
And SecretMethod70, I do enjoy the vocals of Nightwish but my more extreme metal leanings nudge me away from the other aspects of their music. They seem similar to Within Temptation, suggested earlier by meanSpleen. Is it common for these sorts of bands to be fronted by an operatic female vocalist?