I use us car hire Just get the gold package and it includes everything, no sneaky charges. My advise would be to book a reasonable car and then negotiate an upgraded car with them at the desk.

Basically the guys at the desk are on commission, so they will try to get as much out of you as possible. This means the first price they give you will be astronomical. But if you keep saying its too expensive then they should come down in price. Last time we got the staff rate, I think it was 190 dollars to upgrade from a convertible to a muscle car for 14 days