for that size tank (is it 4, 5 or 6ft) I think a Sohal or Naso is a bad idea. They just get way to big for your tank, even the achilles will get to large for the tank especially since they have a attitude and get 8+in. Sohal will get to a foot in 2 or so years and Naso's also get well over a foot long
More then likely A sohal would only last a year or so before he starts killing other fish and get 6+in long, that's with buying a small 1-1.5in sohal to start. Took mine about 8 months to go from 1.5-6+in
I would consider tangs that do not get large and also do not have a attitude.
Zebrasoma family could work.... some can be quite mean thus many times add as the last tang, be it a yellow, purple, scopas etc
You could also do a yellow eye cole tang. Mine is 4-5in and is quite healthy....