Nocturnal Rites?

Everything.

Seriously, though, everything with that singer is really good. Nothing, for me anyway, below a 7.5/10. It's kind of cool to see them develop in order. If you could only get ONE, I'd recommend either Afterlife or Grand Illusion next.
 
Everything by them is good, but New World Messiah is one of their more run-of-the-mill power metal albums.

My favorites are The Grand Illusion and (I'm probably in the minority here, but) Tales of Mystery and Imagination.
 
I think Grand Illusion is their best as well. I also like the new one quite a bit. I wouldn't be unhappy to see them back at Powerfest .. they were terrific the last time, and were a total standout. A lot of the Prog Power folks have beem clammoring for them to be added to that fest, so perhaps some folks would travel this time to see these guys.

Britt