I've tried Achilles and Powder Browns from LFS in the past a long time ago as a rookie and never had success. At the time, I had a 40g separate tank, but only kept in there for a week before I thought they were ok to my 120g display.
A little over a year ago, I tried a Powder Blue from bluezoo mail order, and got a keeper. My DT wasn't ich free since I never QT previous fish, but my Yellow Tang, Bristletooth Tang, pair clowns, mandating goby, pair flame wrasse all healthy for over a year already. This time, my 40g tank was plumbed into same system as display. Also, I kept the Powder Blue in there by himself for 4 weeks, eating pellet and Nori. After introducing to display, yellow tang would chase every now and then but not fight. Also, Powder Blue would get minor ich about once a month for about almost a year, but now healthy and hasn't had ich since then. Probably a lot of luck, but it worked out. Depends on health of fish coming in, but keeping it stress free during acclimation and QT seems tops.