Most any tank would be great with a pair of clowns. Just get the ones you really want cause you can't add more once you get a set. This I learned from experieince.
I wouldnt put a tang in that size tank. Typically they require 6 foot tanks cause they are a very very active fish. My yellow races back and forth all day long, and when I had the other tangs they did the same, especially the kole tang, very active fish.
Some people buy diamond gobies, they can sift the sand but also make a mess of your tank so buy with that in the back of your mind. I wouldnt get one until your tank is mature enough to have food in the sandbed for him.
But there are soo many other cool fish. If you want corals, they have reef safe wrasses, very very colorful. Or if you want the tang look, a lemonpeel angel, not sure if they are reef safe or not though.
As far as corals, you're only limited by space and your lights.
I also agree on the damsels, pull them now before it's harder to get them out. lol They "can" be nasty little buggers.