I've kept a regal in the past. I love the fish, but I would never keep it in a tank that size. Having seen them while scuba diving, I can say that those fish like their space. I'm very against having fish in a tank that they will eventually outgrow or become unstimulated in. Keep in mind that every aquarium we build is meant to duplicate the habitat of the sea creatures we keep. It would be irresponsible to deprive the fish of its bare minimum requirements, those being space to grow and venture around, and obviously food.
Like I said, for now I'm looking at the borbonius anthias, hawaiian anthias, or a trio of flasher wrasses. Thank you for the regal angel suggestion, but it's not happening.