You can look at your situation two ways.
One is that you can just forget about the skimmer for such a small marine tank because you are going to wind up upgrading more sooner or later anyway. A 55 is a good start, but no one sticks with it. Anyone that starts with a 55 usually upgrades in a year when all of their fish get bigger and demand a bigger tank to remain healthy.
On the other hand though, there are some people that say a good marine tank should not go without a protein skimmer, regardless of size, unless you are consistent with weekly water changes. Marine fish are a lot less forgiving them fresh water ones, and require better water conditions.
Me personally, I would have a protein skimmer on the tank even though you are doing the Emperors and stocking the live rock. Once you do eventually upgrade, a well-established 55 gallon tank will be nice to have running because first off, it will be a good tank for your smaller, less "showy" fish. All of the show fish will eventually wind up in the larger tank that you decide to upgrade to. However, if a certain fish is being bullied in your large, show tank, you will always have that option of acclimating him into the 55 to keep him safe.
Remember, you are doing a marine fish tank. The most important thing is that you should not skimp on the important supplies that run your tank. You are trying to recreate the ocean for these fish that you will be keeping. A protein skimmer is a very important thing for any marine or reef tank, and it will definitely help to keep your tank cleaner (that is, if you buy something of value, and not just the cheapest one on the rack).