In STO, you don't chose the exact class when you get a new ship, but the type. Empire State is an assult cruiser type. This type is made up of the Soverign, Majestic and Noble classes. You can swap out ship parts between related classes, or comeplty transform the ship from one class to the other when ever you feel like it. the main body of the ship is Soverign class, but the nacell pylons are off the Noble class and the Nacells themselves are from the Majestic.
I also did this to the City of New York and the Long Island