What do you mean by ///M? X5M (4.4TT engine) or X5 with M-package?
Anyway, for X5M front bumper you will need new headlights (X6 style), fenders, new hood, new fender flares and few other parts behind the bumper.
For M-package you don't need anything else, maybe few other small parts behind the bumper or wider fender flares if you wish.
If I was in your situation I would get AC-S front bumper for about $1000, see picture below.