I agree with aarone ... I would stick with 2 clowns. As for the tang, I wouldn't necessarily recommend it. Besides the space debate that will probably never end, I personally opted to go with a yellow tang in my 55. It did not live. I did everything possible to make sure it was healthy, but it did not make it. However, I know that there ARE successful people w/ tangs in 55's. Anyway ... there are tons of really cool fish that could go into a 55 that would make a great mix! Just keep lookin and researchin. HTH
-Joe-