I wouldn't change the springs as the adaptive suspension is specifically tuned for the stock setup. Also lowering the car may affect some of the drive train geometry in a negative way. I know when I lifted my truck in my 4x4 days it was something I had to take into account. I would opt for the OEM 19" wheels, they hide the xDrive ride height very well.
Here is a side shot of my car with 19" OEM 403s:
and for comparisons sake here is my car with an 18" winter setup. It looks higher even though the suspension is the same:
