In my experiance if you have a "regular" type bike you get more invites to hospitality. Last summer I went to Quebec and rode an old bike that was about the quality of a Huffy. People were stopping me to talk about the bike! Also if you had a cheaper bike it would leave more money for your tour. It would be nice to have extra money for things like dining. One of the glories of a trip to Europe is the fantastic food!

My suggestion is a steel bike. They are cheap and more comfortable to ride on things like cobblestones.