I'm sure you have come to the realization you are getting into bike commuting just as winter is hitting, so you have no time to ease into it slowly. You'd be best off in the long run getting bike specific clothing.

If there is an REI or Performance Bike in your area, you may want to stop by. Even then, you should only take clothing advice from someone who actually rides bikes in cold weather. The right clothing makes a big difference and the wrong clothing is a waste of money.