From everything I can tell it's mainly about having more even heat then, which I'm not sure is all that important to me. I'm not terribly dissatisfied in that regard with what I have now. It sounds like the fan runs more though and I despise that about forced air heat - that blowing noise. Would have hot water heat in a heartbeat if I could. So I may not care for it because of the blowing even if I didn't mind paying more for it. Good to know about the need for appropriate thermostat. The proposal indicates some thermostat that's "included". I was thinking I don't need a new one but if I need one that is right for the furnace then I'll do that.

You may be misunderstanding the terminology. The term "variable speed" refers to the blower in the furnace. So, it is possible to have a single STAGE furnace, with variable speed blower. Your typical (older) furnace may have a multi-speed blower. where the installer 'selects' the required (single) speed through electrical taps. Further, in the above case, the speed of the blower is not variable (i.e., you don't have a choice of fan speed, while heating. As with any gas furnace, the fan speed must be selected, such that the air flow through the furnace will produce a temperature difference (known as temperature rise) of the return air to the outgoing air, within specified limits. What a VS blower WILL do is ramp up in speed if restrictions (clogging filter, poor duct system)prevent the selected airflow from flowing. It will (with proper thermostat) reduce airflow in cooling to increase dehumidification. A 2-stage furnace (also available with VS blower)and proper thermostatic control, provides greater comfort from having longer running cycles. NOTE: A 2-stage unit provides greater comfort, not greater efficiency. Carrier/Bryant produce a 3-stage furnace, which they refer to as 'modulating', but there are larger gaps in output between stages. A modulating furnace provides many stages of heat and utilize variable speed blowers. Again, the ultimate in comfort, but not more efficient than a single stage unit of the same AFUE. You should note that newer furnaces blow a lot more air than older units of the same size. Combine that with a VS blower, if the duct system is not sized for the airflow, the system will be noisy and efficiency may suffer. So, proper sizing and duct system analysis is essential. On a personal note, I replaced my oversized SS furnace with a Rheem Modulating unit (13 stages). Before changeout, the upstairs was always cold; the downstairs would warm, but would chill before the unit would restart. I had to use a space heater in an upstairs bedroom (computer). Now, I have relegated the heater to the basement, and frequently sit at my computer in short sleeve shirts. Insist on a manual J (heat calc) and duct analysis. V

First I would like to see model numbers specifically for the HP condensers quoted. Also the model numbers of the evap coil quoted. What size gas furnaces are quoted? What is your nat gas price/therm? What is your electric price/KWH? You will get a higher degree of comfort with the modulating furnace. It operates in small increments based on heat load demand between a range of 40-100% of output. While the other Infinity furnace is strictly two stages, a low stage and a high stage. My choice would be the modulating furnace and forget the HP condenser and pair with a two stage AC condenser. Both systems would require the Infinity controller for best operation and functionality. At the minimum, I would add a pleated box filter media cabinet. IMO

If you haven't used it on something else yet, both systems qualify for the $1500 federal tax credit which is nice. The 16 seer system gives you a higher seer rating (17.55 as compared to 15.00)which helps during summer months. The HSPF rating is 8.8 as compared to 8.5. BUT - the 14 seer unit gives you a higher heating capacity so less time you'd be using the electric heat strip. Being in upstate NY - I would think you would be more worried about heating than cooling. Typically - the 16 seer system would be a more costly system so it sounds like you may be able to 'make a deal' with the 14 seer system. Ask them for a free humidifier or something of that nature.