It doesn't sound like this is set in stone yet so I'll give my personal opinion - the white painted bumpers gives it too much white - got a preview on the X3s. It is borderline "Pimp My Ride". I would definitely stick with a darker color if getting the m-kit. Also I'm not sure the black mudflaps go...

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'08 X5 3.0si - Alpine White / Saddle Brown interior
Specs: Sport Pkg, Premium Pkg, Tech Pkg, Comfort Access, Aero Kit, Style 433 staggered 20s on Conti DWS
Mods: Carbon 35 tint, LED angel eyes, GP Thunder 7500k fogs, H&R 20mm/25mm spacers, clear reflectors, gunsmoke-tinted taillights
Coded: Digital speedo, windows/sunroof/tailgate close via keyfob

X5 pics at Flickr