I love those wheels! Although as you have monoblocks I can't see what you would want to change them,maybe go for a bigger set.
If you didn't have monoblocks I'd say fit them.
The wheel has just been balanced in front of the original wheel.
It is not fitted to the car.
i dont really see the point in changing to 18's of the same wheel.
The main reason for change was to go for something different while saving some weight and staying oe.