Most important comment: Be clear about whom you are dealing with at the outset; a car rental operator or a car rental broker. 

Don't decide on price alone. The company reputation, age of the fleet, the damage deductible, additional driver fees, etc. are important.

Search the TripAdvisor Forums for advise and traveler experiences with different companies.

      

Car Rental Brokers that operate in Italy:

www.autoeurope.com

www.rentalwise.com

www.carhirelabs.com

www.cardelmar.co.uk 

 

Car Rental Companies that operate in Italy:

www.hertz.com

www.thrifty.com

www.sixt.com

www.budgetautonoleggio.it

www.maggiore.it

www.carsrentalitaly.com