I really want to go to Europe, but I think a full blown tour would exhaust too many resources and take a lot of time.
We really liked the history and modern mix of Barcelona, but we are very amateur when it comes to travel.
I don't have the time to read all 6 pages of this thread, so forgive me if I cover something already mentioned.
Try Quebec city. You know, up in Canada.
They have a very interesting "old city" that will take you right back a century or three, you get the "ooh how foreign" experience of a different language (and if you are polite, they all know English too.) If you want, time it with one of the big festivals in Montreal (Jazz fest, Just Pour Rire comedy festival, &c) and do both cities ... and a nice scenic drive around Gaspe to round it off if you like.
The couple grand you save on trans-atlantic airfare can snag you some nice upgrades in hotels and restaurants, or a few extra days of travel.