We've noticed as we've begun to buy corals at our
LFS that they come on a piece of
LR (sometimes of reasonable size), and we didn't allow for that. If you are going to stock up slowly and not buy all your corals last, that may help.
Also, I noticed that you did what all the books say and left plenty of room on all sides, between the rock and the glass. We did the same thing. Now we've noticed that all the display tanks at our
LFS have rock all the way against the glass in the back, resulting in more room for the fish and coral in front. I wish we'd done it that way.
May I also suggest applying a dark backing (black or navy) against the back of your tank.
Finally, I'd replace the glass heater with a titanium one and if you're going to have a sump, which I assume you will with a 55 GAL, move it there.