There are always aggression issues between sohals and other fish, especially other tangs. Regarding your question, I think some bullying probably would cause dangerous stress on the hippo and powder blue specifically. This is not to say it can't be done but I'd add the sohal last.
On another note, I noticed your other threads indicating you're attempting to upgrade to a 125 gallon. My unsolicited opinion is that you would be much happier with a 180. It would allow you to keep some of the fish that may be borderline or too big for a 125 such as the naso and certain large angels. With a standard 72" x 24" 180 gallon, you would be a lot less limited in terms of livestock.