Was toying with HIDs, but a mate told me that the police are pretty hot on stopping non CE marked kits at the moment. I was very wary of fitting brighter filament bulbs (55/65W) after reading about frosting of lense covers on here.
Have tried it on my K12 and the light is not good. Heaps of brightness but no focus as the centre of the light sit a lot further out than the standard bulb.
If a spacer could be made to ensure the same focus is maintained and still allow the hid bulb to be secured it would be very good.