Not exactly relevent to your question, but I recently requested a Mercedes station wagon from Sixt at FCO. I rent from Sixt in Zurich all the time, so hoped that I would have similar good luck at the airport in Rome.
Unfortunately, they had given away my car and offered me a Fiat station wagon. Not even close in quality, and they did not directly offer me a lower price. As I was traveling with 3 other people, I did not have time to haggle.
Will be calling them this week to see what they have charged me and what I can do. BTW - the customer behind me also had "his" car given away. I had called the Rome station three hours earlier to confirm that they had "my" car and was told "no problem."
fduvall