What is the wattage rating of the the low and high stages? I would think the low stage of the electric furnace would be sufficient as auxiliary back up heat. But in your location it can get very cold and you may need the high stage. Can your thermostat control three stages of heat? If yes then you may want to set it as a three stage system (heat pump, 1st stage furnace, 2nd stage furnace). I am not sure how this works with lock out temperature settings. Call Honeywell for guidance.

dpauley it's all about improved comfort, quiet, and efficiency. Keep in mind, what you and many others call bells and whistles will become tomorrow's standard sooner rather than later. Yes, there will be breakdowns and some components like the var speed blower motor and electronic boards are expensive to repair/replace but reliabilty on top end HVAC is really not a question. Var speed blowers are less expensive to operate because they are DC as opposed to conventional blower motors. Two stg furnaces if sized correctly will save you dollars because you have a low and high output depending on demand and satisfying your stat setpoint. As far as condensers, I am not convinced on the savings here as the large 4-5 ton models' efficiency really drops down to 15-16 SEER, not the glossy brochures that advertise up to 19-21 SEER range. Of course, your location and climate has to be taken into consideration. Ultimately, new HVAC just has to satify the homeowner/family and everyone has different concerns/requirements. IMO

Your friend's work around with the thermal switch sounds as if it was in lieu of a third stage on your thermostat. Honeywell makes a three stage thermostat (3 heat - 2 cool) The TH8110U that would do that for you. And there are others. A bit of an expense though, considering that what you have essentially accomplishes the same thing.

There are several site on the Internet that supposedly have reviews of HVAC, but they are marginal. For the most part, the posts are from people who have complaints. Very few people think about writing a review of their functioning heat pump. As mentioned by Tiger, Trane is also a good choice, and both Trane and the York model you are looking at have the highly desirable "demand defrost" feature. When a heat pump goes into defrost, it is actually air conditioning your house instead of heating it. The heat it steals has to be made up, mostly by expensive electric resistance heating. The demand defrost cuts down on the number of unnecessary defrost cycles. York seems to be serious about the warranty on this unit, offering a lifetime warranty on the compressor. The biggest issue I would have is the supply chain. In our neighborhood, it is about 70% Carrier/Trane. People feel more comfortable that parts will be readily available in years to come with a popular brand. Your neighborhood may vary. Although rare around here, some reliable HVAC companies are picking up the Luxaire brand (same as York) as a less costly alternative to Carrier. That, to me, legitimizes it.