Fish questions/dilemma.

[SteveCGY]

Ok to start off my tanks a 55 gallon 36" long.

Current fish list:
Yellow tang
Clown
Purple dotty back
Blue damsel
Royal gramma
Various snails/crabs.

So I'm thinking of selling my yellow tang as he is getting to big for this tank and adding another clown so they can be a pair. Would this be hard to find a mate for him as he's already like a year old? Should I sell both clown and tang and buy 2 clowns at the same time. What do these two fish generally sell for if I were to sell them? I really don't wanna sell the tang as it adds nice color but it's getting big and I'm sure the tang police will be knocking on my door soon.