Are you just staying at Universal or touring the Orlando area?
If you are just going to Universal, you might want to think about just taking a taxi or shuttle service. Universal charges $15 a night if you are staying onsite to park the car. For a 7 night trip, thats an extra $105. We normally never rent a car just for this reason. You have everything you need on Universal Resort grounds (Tons of places to eat) and most of them are not any more expensive than the other Orlando area restaurants. Of course, if you do not have a car, make sure to tell them at check in and they will remove the $15 a night charge from your bill.
If you are not staying onsite or will be going to more places than Universal, I can not be of much help. Try looking at the car rental companies websites directly. Also, google the company with the word discount and you might find some coupon or promo codes you can use when booking online to save some money. Most of the time (not always, but normally) it is the same price (or cheaper) booking from the company direct. Also, most companies like hotwire and orbits require you to pay in full when booking, but booking from the company direct might allow you to pay once you arrive (or even return the car for the week).