FedEx Gorund has consistantly been the cheapest. Just really make sure of your box dimensions. Sometimes going 1 inch bigger is the difference between $40 and $85 for shipping (bumps it into the next catagory). The size is not on a sliding scale, but rather big jumps, from Oversize, to Oversize II, to Oversize III. As long as it's under 75 pounds weight isn't nearly as big a factor as box size. You can go on the FedEx website and type in the dims and get the rate.
From VA to FL is shouldn't be more than $40 to $50 via FedEx Ground...