It's hard to envision what it would look like. Any of those ideas would work, and you can always find ways to hide equipment. Whichever you choose, try not to make things too symmetric, which may tend to happen with the 2 corner approach. Symmetry tends to look too formal, and therefore unnatural. Putting large structures in the direct center of the tank usually looks odd also. Like anything else in life however, there are exceptions to those guidelines.
One issue you may run into with the 3 stump approach is that a 55G tank has a shallow viewing depth. If you put 3 good sized stumps into the tank, you may not have much of a clear space in the front.
I know this isn't terribly helpful, but just a few things you may want to consider when setting this display up.