Not a whole lot of schooling fish appropriate for a 55. I went through this same issue. Blue reef chromis are beautiful. I do know the blue green chromis are delicate and tend to die easily. Some people think of them as disposable. Grr.
Blue eyed cardinals are pretty neat, and don't look like the bangaii. I have 5 pajama cardinals and while not super active, they do school somewhat.
Someone stop me! Please! But... not just yet...
55 Gal Tropical FW
55 Gal Mixed Reef