QT's are cheap and easy. IMO, they are essential for reef keepers. I almost never add a fish until it has gone through a QT. There are only a few types of fish I don't QT and a mandarin is one of them. I seem to have killed every mandarin I tried to QT. Just take the water from your DT, use pvc for the fish to hide in instead of rock, use some cycled filtration media and some chemi-pure elite and a hang on the back filter like you have. Be careful with copper if you have any angels. I also wouldn't use copper unless you have a test kit for it.
Oh, and Steve made a good point. Be very careful adding all those fish in the QT right away. Personally, I would use multiple QTs.