Actually I would have to say that the clown you do have is an Amphiprion percula not a Amphiprion ocellaris. This is because, the clown you have is much more yellow than the typical coloration of Amphiprion ocellaris, as they are typically a much deeper orange.
So from that I would def. say go a head and get another clown, which my end up being the smart thing to do anyway. If you get them to pair up in q/t you won't have to deal with the possible stress they will put on one another from getting into their 'pairing' fights. And sometimes these fights can be stressful for the fish, and can give the possibility for sickness; a portal for Ich. This is something that you def. want to keep in the q/t as getting in the display system, is a real PITA.
EDIT: Your Entacmaea quadricolor (in this case, a RBTA), looks pretty healthy. The only think I am noticing however, is that it is slightly bleached. Which, with a healthy tank, and stable parameters, should not pose a problem bringing it back to its full health. This means feeding it regularly, and making sure that it is always comfortable.