Yes, the Duke has a point, but I, too, think that the term "dandy" often conjures up images of vanity taken to the point of silliness, and of snobbishness for its own sake. IF, however, by "dandy" you mean a well dressed, well groomed man, then that's a very different matter.
For the latter (and much more palatable) definition, I'd probably go with something like Eau Sauvage, Acqua di Parma, Blenheim Bouquet or Hammam Bouquet -- something that screams "simple, old fashioned, elegant." A dandy (again, per the latter definition) would never wear a "moose on the loose" sex scent such as Musc Ravageur or Rive Gauche or Monsieur Musk, nor would he go for the bizarre (e.g., Kingdom, Fleur du Mâle etc.). He'd keep it simple and understated and ever so elegant (but without being "piss elegant").