I've rented from Sixt several times. Every time I've rented with them, they put a "Hold" on the car of about 2x the quoted price of the rental, which usually falls off in about 7-10 days. For example, last year in Germany with a 9 day hire of a Mercedes E-Class (an upgrade), quoted 960 Euros and charged me in the region of 1800 Euros. I don't like their policy of putting holds on the credit card, but they have the best selections of cars all-round. This is true for all locations worldwide.