Very happy to come across this thread. I am also looking to book tickets in Sept (Munich to Florence). Trenitalia's site is all goofed up. Going with Nachtzugreise for sure. Do have a question... will post a separate thread.

Sorry for the delayed response, but I had seen the low fare from Paris to Rome online but was having problems actually purchasing the ticket so when I called and they offered me the same low rate I didn't ask any questions. I just purchased it right away.