I think in this case the size of the tank is more important. I do not think they will get along in that small of an aquarium long term. I do have them together in my 480 and they mostly ignore one another but your mileage may vary.
I have a Vlamingi, Naso, Yellow, Purple, Atlantic Blue, Hippo, Orange Shoulder and a Sailfin all in the same 265G Reef and no issues. They were all put in at the same time though. the yellow and the sailfin will fromm time to time show a little agression to the othere but even that s rare. Not sayong everyone can have that same mix with no issues.
Well we will see...I might take the risk. I have two clowns and a hawkfish in my current 30 gallon system. Will there be a problem with my current fish and the two tangs?
In my lfs's display tank which is also a 125 gallon tank he had a purple tang and powder blue tang and they were best friends following each other around the tank so i believe you should be fine as long as you add the 2 at the same time