Like everyone said, I'd check out tirerack.com.
Pirelli snow tires are good!
Personally, I have
Yokohama Geolandar H/T-S M+S (Mud & Snow) tires mounted on my stock BMW 18" rims so I can take my X5 up and down the mountain with confidence during winter time here in California (Big Bear, Snow Summit and especially Mammoth Mountain).
I bring the snow chains (as required by CHP) just in case but have not used them with the tires since they performed well enough in snow. These tires are also good for use all year round in all types of weather. No complaints here!
Here's a big photo (towards the bottom of the page) of the tires on at Mammoth during one of the storms up there 2 years ago...
http://www.xoutpost.com/x5-e53-forum/...our-x5-28.html