You really shouldn't have more than one of a type of tang. 3 hippos will likely fight until there's only one left. Different species of tangs will also fight to the death too. The more similar they are, the more likely they will fight. For example, in the tang genus zebrasoma, you have yellow tangs and sailfin tangs, among others. These two tangs (since they are the same genus) are more likely to fight with each other than if you added a zebrasoma and a tang from the naso genus (a naso tang). So if you want more than one tang, try to get ones from different genuses.
Even then, there's no guarantee that more than one can exist in a tank together, they do tend to be aggressive and territorial.
A group of anthias would be a good choice.
Also the poor man's moorish idol you mention is a butterfly fish, as Dustin said. They can be hard to get eating, and are not reef safe. They will be fine in a fish only tank, but not a reef tank.
In a 165, you will have room for a lot of fish.