Yes, everything that you can find in the Character Builder is fair game. This includes all the Power books.
Obviously, since I'm not concerned with the numbers at this point, really the only aspects you probably would need from the books are the specific new class builds I would imagine. Feel free to describe your characters with these eventual selections in mind (like having a pet in your posession if you planned on going beastmaster fpr example).
Obviously, since I'm not concerned with the numbers at this point, really the only aspects you probably would need from the books are the specific new class builds I would imagine. Feel free to describe your characters with these eventual selections in mind (like having a pet in your posession if you planned on going beastmaster fpr example).