Have you thought about the overnight train?? I love it - not sure of the cost, but you save the cost of hotel room for one night. You can get a private compartment for just two, get a wonderful picnic before you board - wine, cheese, etc., and sleep to the gentle rocking of the train. They usually depart in the evening - 7 or 8 PM and arrive in the morning. There are no train changes or anything like that, and you can give your passport to the conductor, who will return it to you when he brings your morning coffee and croissant (maybe you don't need to anymore, what with the EU, etc. Haven't done the overnight in a long time.)

It's one of my favorite ways to go from Venice to Paris.

Callie in New Orleans