I had a terrible experience with Sixt in Germany. I purchased a car with Sat Nav. When I realized 10 minutes into the trip I needed to load a CD, I found out the CD was missing from the case. Every other country OTHER than germany was available. In the next town with a Sixt we stopped in and explained. They dismissed us right away and said there was nothing they could do. They did not even offer to call the original site to see if they had it. Looking at a card in the glove compartment a note was made that the CD was missing yet they rented it again.
Buyer beware I guess.
Oh and I had to call 3 times afterwards to get a partial refund. To their credit they did give a partial refund on the third try