No doubt the bannerfish are beautiful. I just think they get too big for your tank. In any event, if you do add them, I would not add any other big fish (tangs, etc.) until you've gotten some feel for how much space these guys will take up when they're grown.
I had a pair of adults before and they were just fine in my opinion. Between a crazy lunare wrasse and an a relative who thought they could clean the tank with bleach I lost them (and all their tankmates besides the wrasse), but never did I feel the tank was too small for them. They lived with a yellow tang, a purple tang, a copperband butterfly, and a pearlscale butterfly and all of them thrived together.
I hope the clowns maintain the detente they've achieved in your current tank when you move them and disrupt their territories. I'd keep an eye on that situation.
Why would I move them? They are in the display and have been for quite a while...?
Finally, I would skip the cleaner wrasse. I missed that before on your list.
I had excellent luck with a cleaner wrasse from Quality Marine, until the safety cover got knocked of the koralia... When I get another cleaner, I will make sure it has been in the store for a while, is greedily eating, came from Quality Marine, and will go through a 6 week quarantine.
I like my tank. It is a challenge to keep clean, particularly around the sand bed, but I love the space - it allows for some interesting aquascaping.
Ya, the dimensions are a challenge when it comes to cleaning, but the aquascaping potential is just awesome.
Good luck.