I've got to replace an old (17+ years) condensing unit and gas furnace in my home in Atlanta, GA. I'm leaning towards a Rheem 90+ modulating furnace with a dual fuel link to a heat pump.
The advantages as I see them are: 1) the HP will be at least as economical during the cooling season as a straight cool condenser; 2) the HP will be more economical heating in the 60-40 degree range than a gas furnace, given gas & electricity prices for the foreseeable future; 3) a modulating furnace will give me better efficiency during the below 40 degrees time of year, and 4) the variable speed blower will give me better comfort during the cooling season and the heating season than a single speed blower.
The disadvantages as I see them boil down to greater upfront costs than a straight cool c/u + standard 90% furnace, and a greater likelihood of service calls because the system is so complex: dual fuel boards, modulating gas valve, variable speed blower, all of which would (presumably) be expensive to service/replace after the warranty runs out.
Is this kind of system overkill in a practical sense? I love the idea of the variable speed blower for both seasons, but do I really need a complicated modulating gas valve when the furnace will only be running at temps below 40 (and then at a fairly high rate, I assume)?
Should I default to a straight cool c/u (eliminating the dual fuel complexity and upfront costs) and hope that a 90+ modulating furnace is so efficient that I don't spend too much more in the 60-40 degree season than I would with a HP?
Any advice would be greatly appreciated, and feel free to point out any misconceptions I have about any of this stuff. I'm a classic example of "a little knowledge is a dangerous thing."