As Fapout mentioned it depends on how low you go. If you lower it to the height of a 335i w/ sport suspension I think you would be ok from the fact that I haven't heard of too many 335i owners complain about ground clearance.
That being said I had my old B5 A4 on coils and hit a lot of ice chucks left in the road. Every time I hit one I would cringe and hope the oil pan was still in one piece. My A4 sat lower than a 335i though.