Greetings Cordcutter,
Can you rerun your tvfool signal maps with heights of 20, 40 and 60 feet and link them?
We need to see if there is improvement in signal at the greater heights so that gives you a shot at Knoxville (magnetic 106).
Any early front runner in your needs is one of the HBU series by antennacraft, either the HBU44 or HBU55. Winegard makes good antennas too, a Winegard HD7698P might be a good fit as well. These support high vhf (channels 7-13) and UHF (14 and up), which is what you'll need.
http://www.antennacraft.net/Antennas/AntennasHBU.html
http://www.winegard.com/offair/fring...f-antennas.php
Cheers.