lots of snow = avoid the 20" tires from factory which are likely Dunlop SportMaxx summer tires. But with an '08 or '09 I'm not sure how many still have those original summer tires - depends on mileage. You can always swap to all-season 20s if it's not deep snow and don't want to give up the look. Personally I don't like the idea of swapping wheels twice a year and having to store them, or giving up the look for so many months. I've done perfectly fine, here.

Definitely do the sport package from those years though, as it includes adaptive drive.

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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