WOW!!! She's exquisite, Amy!
I'm a name snob, and normally dislike the "sire + dam" naming protocol...
...but I love Step Brightly!
It suggests a beautifully moving driving horse.
Adding Firenza to it doesn't work for me -- it sounds like a compromise -- which is never good. I would use Firenza or Firenze as her barn name.
But, as I said, I'm a name snob, and this is (obviously) just my opinion. By any name, she's DDG -- Drop Dead Gorgeous!