Where in Pennsylvania, to where in Florida? The cheapest I have found, is Amtrak, which will take 500 pound pallets. That would only work if it was close on both ends. There are professional packers, who will pickup, pack, and deliver to Amtrak.
Two, craigs list, Moving from PA to FL? I have a deal for you. It is cheap to list, and you can find someone you can check out.
I would say it comes down to how much do you have, what is the largest piece, which method would be best.
Nothing is cheap, fly up, rent a van, hire someone to load, take the car train south, it will cost $1000.
Tagging along on someone elses moving, maybe a few hundred.
Post an offer on Craigs list, what volume, and where you want it. You can always say no or not respond, but you might find someone coming that way, and you can pay their gas.
I wish the car train ran east west, I hate to drive across Texas.
Good luck!