The dwarf angels are unpredictable like that, they will live peacefully for months or even years in your case Kass03 and then one day they change and start picking on other fish or corals. Its a pretty safe bet that they will be fine in the 150 though dont be surprized if they do fight. Your planning on putting three in and in my experience with fish thats a better move than putting in to, cause even if they do fight there will always be the odd one out. I'd do it if it were me.