The car rentals I know are Avis and Budget. They are reliable too.
Budget is little less costly than Avis. But Avis gives you more. You can go to the web www.avis.com and calcualte how much it costs after you choose the type of vehicle, base days, date of pick up and delivery. Selection of Insurance counts a little bit. You can even add some extra accessories if you want.
In case of Avis, age might be one of the barrier. If you are between 21-24 , I guess you gotta pay $27 per day as underage rental to the total amount. Even you can't rent vans,trucks and luxury cars if you are under 25. You are saying that you are travelling from one state to another. So, on vans, SUV or trucks , they charge you $0.29 per mile whereas small cars have unlimited mileage. It all depends upon your age, selection of vehicle and your total days of rental.
I am moving from GA to MN and I am choosing Avis this time.
Just sharing my experience. You can even go to www.budget.com for Budget info.
Have a safe journey !