Ryan,

I'm in Maryland and work in DC, but not as an HVAC professional. You can click my name and send me an email and I'm happy to talk about specific companies and give a recommendation or two.

First, in our area, I don't think 90% furnaces are necessary if going with a heat pump, especially since the PVC pipe venting can add a bit to the cost of installation. I think a heat pump and gas furnace is a good move to have some flexibility in fuel source and costs. It's a guessing game without specific model numbers (as far as whether it's builder grade, top of the line, etc.), so ask for those. A model number would look like 13HPD-024, for example. The fact that your sizing varies presents another issue--did any contractor do a formal load analysis or are both guessing? Equipment that is too large (or likewise too small) will not run as efficient or perform as well as properly sized equipment. You are correct about the D.C. area. Large, established companies tend to be expensive here (as they do in other areas), but there are a lot of small, fly-by-night companies that do dirt cheap (price and quality) work. I would find a reasonable company whom you trust and think will be around to do business with in the long term. Around here, depending on what you are looking at, price will likely be in the six, seven or eight thousand dollar range (and up if top of the line system and controls).

Before you sign up with the first contractor, verify if Lennox requires a yearly service contract for the 10 year parts warranty to be in effect. I find this suspicious. I also recommend getting a 10 year labor warranty directly from the manufacturer if possible.

Carrier does not require a yearly maintenance plan.

@Ryan
Thanks... I don't see a way to email you by clicking on your name. I think you're probably right about the furnace efficiency, especially since I would only be using the gas for heat probably just 2-3 months per year. Getting the model number is also a good suggestion.
Both contractors did careful analysis based on dimensions, windows, insulation, etc. They reached different conclusions. Thanks for the hint re: price range. Both companies that gave quotes today have been around for years and are pretty well known.

@mike_home
Maybe "contract" isn't the right word. I wouldn't be committed to a maintenance contract, but my warranty would depend on it, so in a way I would be committed. The warranty does seem a bit weak, especially if I'm paying them to service the equipment every year. It seems like a fair expectation that I shouldn't have to pay for any repairs if they are checking on the equipment every year.

The 10 year parts warranty comes from the mfr. Parts only. No labor. The installer typically provides a 1 year labor warranty. You do not have to get a maintenance agreement from the installer for the mfr's parts warranty.

An optional 10 year PARTS AND LABOR warranty typically requires a maintenance agreement.

Take care.

I have Carrier Infinity furnaces and condensers. I have the 10 year parts and labor warranty from Carrier. The contractor I used is a Carrier Factory Authorized dealer.

I was told by the contractor I am not obligated to pay for a yearly maintenance agreement. Carrier will pay for the parts and labor for any repair. The only warning I got was I need to change the filter when needed. The contractor told me he has had customers not change filters for long period of time and then needed repairs needed under warranty. There is a risk Carrier would not pay for the repairs if they felt the equipment failed due to lack of maintenance.

You have to decide whether the $140 per year for annual maintenance is worth it or not.