Do you have a sponge filter in your DT/sump?
Ideally, what you would do, is set up a new tank...do a water change on the DT...put the water and the sponge filter from the DT in to the QT. You have your bioligical filtration from the sponge filter and already cycled water. Top off the QT with fresh saltwater, just like it would be a big waterchange. Put the fish in it before you top off and you wont need to acclimate them first.
What I did, is, I set up a fowlr tank for my qt tank. That way I have the rock that keeps the bioligical filtration going and I can treat it with copper and other meds if needed. I run carbon and a small intank skimmer and a two bubl t-5 light. I just keep it simple.