A lot depends upon the look you are going after. Each style/finish works on a silver, which is good. Each look has a grill style/finish that works good or better with it. I would also add silver/body color as an option. The right grill could look rather clean painted in body color, esp. on a silver one.
(I look at this from the perspective of a silver owner who has contemplated LOTS of looks for silver xB2s.
Tell us more about your longer terms intentions and what look you are going after.