Well, when I worked at the fish store heres how it went down.
They had Ultra grade, 1st grade and 2nd grade.
Anything "Ultra" grade was usually what you wanted as 2nd grade SPS were brown, LPS were boring and so forth... first grade got you some decent colored stuff... nothing too exciting at all really.... and ultra grade is anything decent or awesome you see now. Big price difference also. Also, this is from the wholesaler.