Taylor,
You can go either way and find good deals. Sometimes warranty issue come into play when you buy a used bike as most manufacturers only cover the original purchaser. There are situations where shops and their manufacturer reps will work with other than original purchasers to resolve issues. A Madone is a great bike from what I have heard from friends that ride one version or another. All of the major manufacturers have all levels of bikes and the Madone is the upper level so based on the possible cost, you quite a few options. I would recommend going into a local shop and seeing what is available and what may appeal to you. We have two shops hear in Fayetteville, Hwley's Bicycle World on Raeford Road and The Bicycle Shop. If you like, I can meet you at Hawley's on Saturday afternoons from about11:30 am to 5:00 pm (I know that tomorrow will likely be a bad day to be out dur to the weather) . Hope this helps a little.
Robert