any advice for getting from Nashville to Philadelphia?

[Rasputin]

I would suggest Birmingham - Nashville depending on the bus schedules.  I used to do this once or twice a year but that was to connect with the Southern Crescent so my experience is a bit dated. 

I went Nashville to Greenville, S.C. by bus once to connect with the Southern Crescent but that was a long day (made a bit longer by a Greyhound strike).