What do you mean by a Regal Tang (I couldn't find it on this web site)? Is that another name for hippo tang?
I would highly recommend a hippo tang. We have a similar set of fish - 2 clowns, a yellow tang, a sailfin tang, a neon dottyback and a mandarin. The hippo tang is one of my favorites, if not my favorite. Next to the clowns, it's the least shy and has funny behaviorisms. The only drawback is that they're apparently a bit sensitive to parasites. Ours had problems initially, but with the help of the cleaner shrimp, has toughed it out - which was basically the advice our LFS gave.