CDW is mandatory in Italy - by Italian law it is included in each rental. So while credit cards in the US often cover overseas rentals as Primary Insurance (as opposed to credit card coverage on US domestic rentals as secondary to your own Allstate/StateFarm etc).. Italy is a moot point. CDW is mandatory and included.

You could try autoeurope.com - I have used them for a lot of rentals - they actually are a booking agency - with negotiated rates.

But the issue here - is you want a cheap car for one day and you are paying for a intercity fee (that is rental based) and taxes that are percentage based. I don't think you are going to come out much lower. We rented in Italy -and I would say for a mid sized car (all Fiat or Alfa there) it is about $80/day even for 5-7 day rentals.