2005 X5 4.4i NonSport (Stock 18" Wheels)


I'm at 45,000 miles on my first set of tires (yes, my wife is the primary driver ) and I'm about to head into winter. I've seen people reference Blizzaks and the Pirelli Scorpion snow tires. If you have mounted snows on your X can you please tell me:
1) Best snow tire to buy?
2) Where is the most cost effective place to buy them?

TIA,
Chris