I have been looking into getting a winter commuting bike and I am not too sure what to get. I live in the DC metro area and we tend to get more ice and wintery mix than anything else. I currently commute 10 miles to work each way on my Trek Madone. I know that using the Madone in the winter might not be the best thing for the bike given the conditions. I have read in quite a few articles that single speed bikes are a good option. What is everyone else riding? what do you suggest? My budget is $300 -$400 and I am open to any suggestions.

Thanks in advance!