I would look at the
Fridmani(Orchard Dottyback) Dottyback can be somewhat aggressive but shouldn't be a problem with what you have.
Sunrise Dottyback-Not that aggressive and very active.
Cardinal Fish, you could even get a pair
You probably want to look at some of the smaller wrasse and maybe an one of the many different Blennies.
If you're going to get a Naso I would get a small one as they do grow to a pretty good size and need plenty of swimming room. I wouldn't worry to much about the Purple bothering it.
Don't forget you have a reef tank and you don't want to load it with to many fish as it will put a strain on your bio-load in the tank. For that reason you may want to pass on the larger Naso and go with a smaller fish.