if you really want a tang, the kole is the only one i would consider. there are so many fish that are better suited for your tank and i think a lot of them look a lot better too, but thats just my opinion. i think a lot of people jump on the so called "tang police" because most of them have only seen the yellow tangs that go in and out of there local fish stores. if you have actually seen a full grown yellow tang than you would see my point. they are no where near suitable for a 55 gallon when full grown. and if you dont plan on keeping the tang till its full grown, then imo, you should not be keeping fish.
i was just at my local public aquarium. when you enter the door, there is a pool that has about 10 or so stingrays and a few smaller sharks in it. there is also a school of small yellow tangs( about 2-3") and they swim this whole pool. the pool is about the size of an average living room. now, take a clown fish or some other type of small fish, i can guarantee they wont swim that whole pool. my point is that tangs enjoy a lot of swimming room, and they are best suited for a large swimming area. there are plenty of fish that dont need that much room and these are the fish one should be considering. imo.
and personally i think a lot of people need to think before they talk.