Before you concentrate on a brand, you need to verify if the contractor will do a good installation. Are you talking to an HVAC installer who will do the work, or a general contractor will arrange to "install any brand"? It sounds like you have two furnances and condensers for a two story home and you are only replacing the units for the upper floor. Has a Manual J (heating/cooling) load calculation been done. A 2 ton air conditioner for a 1900 sf top floor seems undersized. I have never been to Tennesse but I assume you hit summer highs in the upper 90s. In terms of brands the upper tier are Carrier/Bryant, Trane/American Standard, Lennox, and Rheem/Rudd. I don't have experience with Frigidare (which also may be Amana), but again brand to secondary to a proper sizing and installation.

Some of the ductless systems are very efficient & you can run more an one blower with coil off one condenser. That old furnace and duct system might not be very efficient. - udarrell Here is a link that might be useful: Cut Utility Bills in Half

All true, Austin. My first objection was to the post that appeared to say that you lose any setback gains when you are in the recovery mode. You post appeared to accept that and I found it hard to believe that you do given what you have written in the past. That is a really annoying urban legend that I believe can be traced to early heat pump installations with very simple controls that could not recover from any really heating setback without hitting the backup, electrical resistance heat strips. That was fixed, obviously with better thermostats. Things they are a'changin, however. One important point is that with variable speed systems, maximum output puts you in relatively inefficient operation. That has led some writers to advise homeowners similarly, don't do setbacks. In fact, that is too simple. If the setback is deep enough and of long enough duration, the building characteristics lead to high loss, and you are not too close to the outdoor design temperature, setbacks can still be useful. The trouble is that most homeowners are not able to make the judgement. Many HVAC pros probably can't do it either. The fact is, to determine what will work best requires the kind of calculations that HVAC engineers are used to making and some good starting data. That is why the cooling equipment makers of the HVAC industry needs to get on the stick and catch up with the boiler makers (and probably furnace makers) who have relatively elegant controls allowing efficient setback recovery at partial output. They make it work, so can the cooling equipment gurus. Eventually, we should be able to get to the point where someone can look at their thermostat, or home computer, and see a message from the system telling us that it has decided that due to the weather forecast, it is not doing a setback today because it won't be able to return to your comfort level (conditions too close to outdoor design temperature). Those heating systems (mod cons) can take advantage of require considerable set-up and tweaking although I think that they are getting better at self-learning. Some are so adaptive that not much or any learning is needed to operate pretty efficiently. If anyone is not familiar, here is an example. I am making up the concrete numbers, but they are probably not too bad: The boiler starts up to recover from a setback at 60% output. The controls know the outdoor temp and the target temp and have already determined what time to start the recovery to have the floors warm by the time pop usually gets up (before the kids and wife) to get to work. Uh oh, the temperature rise is not as expected after 30 minutes so it bumps output up to 80%. After another half hour, still not good. It is a little too late for dad since he is leaving a little earlier than usual today, but it bumps output up to 95% and makes it time for mom's feet to hit a warm floor. (OK, efficiency has dropped from 97% to 92% for that last 30 minutes, but no biggie.) Cooling systems have the ability to look at outdoor temp and determine start-up time, but the modulation, on the fly or not, is not there for residential systems as far as I have seen. I'll be optimistic and believe that we will get there soon.

Do you have a basement so condensate can run down? I have no experience with pumps to push it up, but that should work. If possible, I'd install the drains through a closet or something by placing them near the closets. That way you can get to them in case there is a clog or leak. You might consider covering several areas with the small, flat AHUs that connect to short ducts. I do have some advice for how to combine indoor and outdoor parts. Smaller systems are convenient in the case of a power outage because you can run parts of it with a smaller backup genset. In addition to that, group indoor units that will be running at times with low demand, low output, together. That way the outdoor unit driving them can modulate better rather than toggling on and off. i don't know why refrigerant lines in the attic would be a problem, but keep them as short as practical.