You need four with all FWD. It is dangerous to drive on front wheels only.
The best winter tires IMHO are Michelin X-Ice and Bridgestone Blizzack WS-60. I suggest peeking at tirerack.com for great pricing and check into separate (steel) rims as they pay for themselves in one season.
I will add a great inexpensive alternative are Firestone Winterforce. They can be studded(improves ice traction but expense of noise) but have incredible performance for the price and decent life.