Enterprise still has decent prices, but get the car OUTSIDE OF MARION COUNTY. We rented from just inside Johnson Co and saved tons of money.
Also, talk to your Automotive insurance agent to see what coverage you really need. Enterprise is one of the better companies in what they won't come after you when a collision occurs.
Avis usually seems to be the cheapest for us at work. I also agree to check with your insurance provider. You probably don't need to waste the money on extra insurance. Do a Google search for coupons and you'll probably find some that will work.
Check the online "travel" sites... Orbitz, expedia, travelocity, yahoo travel, etc etc.
Shop around, find a decent rate.
THEN go to the company's website and duplicate the search. You'll often have less expense that way because you're not paying the website any money to keep their doors open.
I'd even stop by a place or two to get a price quote.
Just don't get it from anywhere near the airport; they'll gouge you on convenience. And, as indyjoe said, try getting quotes from a place not in Marion County. Marion Co, as do most large cities, have a heck of a tax on rental cars.
And please, check to see if your current auto insurance covers you while you're in a rental. I know that mine does. If so, then don't give the rental company any more money for their "insurance".