We drive from Louisville at least once a year....we have tried all kinds of stopping places (we have driven straight through and stopped at LOTS of places enroute). The spot that seems to work best for us is Macon, GA. It is about 9 hours from Louisville and an hour south of Atlanta. From there on in to WDW is an easy 6 hours the second day.
The main thing to consider if you will be travelling on a week day is to avoid Atlanta between 7:30 and 9:30AM and 3 to 6PM or so...it will easily add an hour or more to your trip if you hit it at the wrong time.
We usually leave home VERY early (like 5AM) I know that is a little nuts, but for us it works well, DH is definately a morning guy and the kids get in the car and go right back to sleep and we are usually past Nashville by the time they wake up and want breakfast. By leaving that early we can get to Macon by early/mid afternoon and can unwind a bit.
We have had good luck with Priceline hotels in Macon....we have always gotten a really nice LaQuinta that has several good restaurants nearby including an Outback. I always bid in the Macon North or Macon West Zones for a 2 star hotel. If you prefer to book directly it would probably be about $70 to 75/night. It is the nicest LaQuinta we have ever used, easy interstate access and felt very safe to us. (It is in the Macon North zone on Priceline, but there are some nice clean, safe places in the Macon West zone as well).
We like to get past Atlanta so we don't have to tackle that the next AM and we have not had much luck finding any decent places to stay between Macon and Valdosta.
If you are leaving Louisville late in the day and just want to get a head start and do the bulk of your driving the second day we usually stay at Dalton, GA ... it is just south of Chattanooga. Not too many acceptable places to stay in Chattanooga that are easy access from the Interstate that we have found. Dalton is about 5 or 51/2 hours from Louisville.
It is not a bad drive....everytime we do it we always feel like it was faster than we thought it would be.