I think a 650c front and 700c rear wheel is a really bad idea! What happens when you want to upgrade your wheelset to something nicer? I've never seen a wheelset with different sized wheels in it so it would be really hard to do. Out of the bikes you listed I would go with the Lemond for sure. I ride a Buenos Aires and have been really happy with the bike. It may be a little more $ then some of the other brands you listed, but worth it IMO.