There are a ton of cichlids that would do well in a 55 with your danios...just stay away from Malawian cichlids and larger SA/CA/Tanganyikan cichlids that might conisder them dinner.
Some options include keyholes, bolivian rams, rainbow cichlids, blue rams, flag cichlids and their kin (any Laetacara), kribs, A. thomasi, apistogrammas, etc. Essentially, any dwarf SA or African riverine cichlid. All of these also do rather well in a general community tank and are not primarily piscivorous in nature. Angels might even work - they sometimes snack on skinny small fish, but not always and danios are a tad bigger than neons.
Eric