Jackofall1, the OP lives in Mid-Southern IL, so in reality, a Heat Pump would be a better solution, with Geo-Thermal being the best. His supplier is a part of the Touchstone Energy group, so they are best to find out what rebates are offered, and then go from there in what gives the best payback for the long term. Especially depending on how long they plan on living there after they install the new unit.
Since it is a rural area they live in, I would opt for a Hybrid Heat-pump, or Geo, before going with a conventional system.