You also want to check out Doctor Butcher (not to be confused with the hip-hop artist of the same name). It is a disc Jon Oliva and Chris Caffery did after Chris Oliva died. Caffery did a fantastic job of guitar riffing.
I think it was kind of a catharsis of Jon as the lyrics are pretty aggressive and dark-ish. However, it is awesome. Whenever I'm in a pretty cranky place, I give this a listen and it lets me get my aggression out. Was a great catharsis for me when I lost someone.
Dr. Butcher - Season of the Witch:https://www.youtube.com/watch?v=q-QEiCYwfOM