Eeeeeeek.... I bought one, promptly returned it to the store. Most people here would advise against them, although there are a few diehard fans out there. Skimmer for you: will it be hang on back, or in-sump?
If it's hang on back, I would suggest an Aqua-C Remora Pro with Mag 3 pump. Other people like their bak-paks, but might be a bit small for a 55.
If it's an in-sump model, the choices are MUCH wider.
~~Rob