I personally don't think that a 55 is required for dwarf lions. I've got a Fuzzy in quarantine that's going in a 45 tall. I really don't even think he'll be cramped if there are only a couple of other fish in there. I mean, my 45 is the same depth and height as a 55, it's just one foot shorter in length.
I may change my mind when mine grows out, but I think if it were the ONLY fish, you could probably fit any of the dwarfs in a 40gallon or maybe even in a 30 if you had really great filtration.
As always, this is just the opinion of a newbie.
Later,
JAM