Clical music recommendations?

Hey everyone, I was just hoping some people more experienced than I might be willing to give me some clical music suggestions. I'd like to get into it, but it's not a genre that I'm really familiar with and it's so broad that I'm not quite sure where to begin. I was (pleasantly) surprised to find that I actually like listening to it when working out. Usually I listen to rock and rap when I'm exercising, just because the high-intensity beats keep me going. But I have a couple of clical and opera songs on my mp3 player, and when I listened to them at the gym I found them kind of calming and stimulating at the same time. So, if anybody has any suggestions for a newbie, I'd really appreciate it! I'm not a big fan of piano pieces (at least not while working out, which is when I usually listen to music), but any, I'm not sure how to put it--big, symphony-sounding pieces, or primarily string pieces would be greatly appreciated!! Thanks in advance to all, and happy new year.