$85/day sounds like a lot for a basic vehicle at BNA airport. I think you can do better. There are lots of coupons and discount codes available. For companies like Hertz, Avis, Budget, Alamo, National, you can stack both a discount code and a coupon. Dollar and Thrifty (both owned by Hertz) only support discount code
or coupon code. Enterprise supports discount code only. AutoSlash makes the process of finding the best discount and/or coupon code simple by taking you through a mini-interview process about your rental details and what groups and memberships you have to find you the best deal.
Also keep in mind that the best deal today may not be the best deal tomorrow, or next week, or even the day before pickup. Rental rates can change multiple times a day. In order to truly get the best deal, you'd want to keep checking rates, or use AutoSlash's free tracking service to be notified when a better deal comes along.
As far as companies go here's a
handy guide to company ratings we put together.
Lastly, it sounds like you probably want an intermediate (midsize) car or larger. You should probably also look at intermediate and standard SUVs. They can be very price-competitive with cars depending on the situation--sometimes even lower in price, so worth checking.