I agree with previous post. Some installers will try to charge alot more extra, but don't fall for it. Might cost a bit extra based on my recommedations below. I'm in NE ohio also and did the same as you nearly 2 years ago (I upgraded my central AC to a heatpump. I didn't upgrade the gas furnace). Heatpumps do a great job of maintaining temperature. They are very efficient in milder temps (30 and above). They are a smart upgrade in are climate. Why just buy a piece of equipment that only is used 2-3 months a year when you can spend a bit more and possibly use the equipment much more of the year. They also provide even heat since they run longer at a lower output temp. I find the rooms to be heated evenly and are comfy. If your place is decently insulated and not drafty you will be able to heat with the heatpump down to very cold temperatures if you don't mind it running nonstop. I switch to the gas when very cold or when sleeting and snowing to prevent the heatpump from going into defrost. Defrost isn't exactly wonderful. If you have the gas backup thats when it comes in handy. It will make your heatpump last longer too. I recommend the honeywell focus-pro thermostat kit. It has an outdoor temp sensor. You can program it to automatically switch from heatpump to gas based on any outdoor temp in 5 degree increments. This kit costs a bit more, but its worth-it. It saves installer time in setting up system and its nice. I love having the outdoor temp on my inside thermostat. A very nice feature. My HVAC guy was able to purchase the programmable focus pro wirelss kit withoutdoor temp sensor for $229 at his HVAC supply warehouse. Some try to charge $300. Make sure you get a heatpump with demand defrost. Go with highest efficiency single stage. I would personally stay away from goodman but thats my opinion. Others like them. If you need any help, I can recommend some installers that are quite resonable. FYI - Luxaire makes some nice heatpumps that are quiet, with demand-defrost, and very reasonably priced. They have scroll compressors, insulated jacket around compressor. All installers in this area should be able to get those.

With reasonable electric rates (which I assume would be cheaper to operate a heat pump with than an 80% gas furnace with your gas rates), and a mild winter climate, a heat pump would be a good option in my opinion. You can keep the gas furnace for backup, though it may not see much use, and doing so would not allow you to leverage the tax credit since you'd need a variable-speed fan which boosts the efficiency for higher SEER equipment. What you would potentially install is a heat pump and a fan coil inside, and that would take care of the heating and cooling and could keep you the tax credit if you choose the correct components. A contractor should come to your home and discuss all this with you and hopefully do a heat loss/heat gain calculation to determine the correct size equipment. I'll attach the link below where you can see what is a rated match (just a tip: keep the model numbers as simple as possible; for example, a Trane may be proposed as 4TWX5036A1000A, but in the database it only reads 4TWX5036A1 -- if you are having trouble finding results). The first link is for air conditioners, and the second for heat pumps. Your 58STA is probably not in the database because it isn't variable speed. Just so you see how it works, look at heat pumps and type in 4TWX5036 for outside and 4TEE3F for inside, and you'll see possible indoor fan coil matchups and their ratings. Here is a link that might be useful: AHRI Directory

for Speedymonk speedy, I live in Southeast and also have a dual fuel Trane-same as yours, XL14i(R-410a) paired with an XV90 furnace. I really wanted the XL15i but it was just being introduced and only available in R-22 which I did not want. I probably should have gone with the XV80 furnace but kind of hedged as this was my first experience with a HP. I knew though that all was OK since my wife has never complained about the HP since it most likely performs about 90+% of heating chore based on my area's climate and relatively mild winters. I estimate I used about 60-70 therms of nat gas last winter. Savings over 100% nat gas heating vs heat pump heating est at around 35%. No regrets with the HP. Trane though is really falling behind in tax credit qualifying condensors both AC and HPs. IMO

The DOE has worksheets that can help you calculate the relative cost of heating and cooling with different systems using your current energy costs. Of course you need to predict the relative costs over the next decade or two to really tell what is best. How is your crystal ball working? I would like to clear up a couple of common misconceptions. One type of heat does not dry a house in the winter any more than another. Leaky house envelopes dry houses. Heat by flame of some sort might dry a house more because they draw more outside air in if there is not a source of outside combustion air. That would be the only mechanism. There is nothing special about heat pumps in poorly-insulated, leaky homes. No heat or air conditioning source works as well in that situation as well as they do in tighter, well-insulated homes.