I think Bicyclebluebook.com always lowballs prices for used bikes by a few hundred. Statricks.com is usually much closer to the true value for used bikes since their prices are based on recent listings for used bikes.

For a 2007 Trek 1600, Bicyclebluebook.com indicates $300-455 while Statricks.com indicates about $600-900 depending on condition. The prices on Statricks.com are more consistent with the prices I see on our local craigslist. The Trek 1600 is probably comparable to today's Trek Lexa. If your bike has Ultegra or 105 components, I'd indicate that and also mention a Trek Lexa with only 105 would run about $1600+.

Here are the links for both sites for your bike:

http://www.bicyclebluebook.com/searc...spx?id=3029528

http://www.statricks.com/blue-book/r...-trek-1600-wsd