X, I love the Achilles and had one that ruled my tank for 5+ years (plus the previous owner had him another 2)....They are wonderful, beautiful, active and personable fish. Mine was the most aggressive tang I have ever seen though, he was brutal to new fish, and killed a Yellow Tang I tried to add. Mark Martin (whom owns a rival online site) feels the Achilles is inch for inch more aggressive than even the Sohal. Just keep in mind an Achilles will likely need to be the last fish in and I would scratch the Powder Blue from your list if I were you.