Grats on upgrading, it's always fun to do and you can get a whole new stock of fish! LOL
If the tank is a standard 75 then the tang should be fine in there. I would however caution you about the copperband butterfly. They typically will do best in an established tank and are very difficult to keep for the most part.
I have one that my LFS
had been training on frozen foods for a few weeks but in any other circumstance I would NOT have gotten it. They can be really tough to get eating, mine eats by hand which is cool but is time consuming. LOL
As far as other fish what did you have in mind? Happy tank mates or aggressive? Since you said Reef then angel fish are out as they can nip coral. How about a nice size blenny, like the midas blenny? Could also add some chromis to get some schooling going on and add some zing to the tank.