Man, you guys are awesome. I expected to wait at least a day for someone to respond. Let me try to answer the questions: 1. Where do I live? In Maryland, between DC and Baltimore. You guys know better, but I feel like this climate is split evenly between running AC and heater 2. Dealer reputation? One is very very large regional with a good reputation, but like all Companies that scale, you can find unhappy customers if you look. Other is a state company referred to us directly. Small sample size, but two references were solid 3. On thermostats, both two stage proposals come with new thermostats...the 1 stage uses existing. so hopefully ok there 4. Existing furnace is 120K BTU 5. The Carrier quote commented on the ductwork, but really didnt dig in. The other guy noted it. When, and how, should I press on what needs to be done. Are they inferring nothing needs to be done? Hard to imagine they would miss a chance to charge for more services 6. Load calc...do they do this? how much do they charge? 7. Carrier 1a - 100K, 1b 80K. Lennox 2 - didnt write, but i think he said 100K (second speed at 60K 8. Did i misquote the model #s for all the coils? 9. They both mentioned the filter cabinets, vaguely, and said they were ~$50 and would be replaced annually. Hopefully I gave the answers to get more responses. Thanks again in advance. I truly appreciate the help

Thank you both for the replies! @mike_home: Perhaps because I usually set the AC temperature to be 77-78F, at times I do feel a bit uncomfortable on the 2nd floor when the outside is only moderately hot. The 2nd floor doesn't go below 80F. Therefore I can't be sure whether humidity contributes to the stickiness on the 2nd floor. Maybe a little bit. But I'm hoping the variable-speed blower can help and I don't have to pay more for the 2-stage AC. @tigerdunes: The contractor's proposal says the systems qualify for federal tax rebate of 10% of the total cost up to $500. I'll be sure to get a thermostat with the cool to dehumdify function. The contractor said 95% furnace would need PVC flue piping. I'm not sure what that meant, but I guess I should just get a quote for XV95 with the PVC flue piping done.

You can still keep the Infinity interface with the Performance series outdoor units, so it will still do an adequate job with dehumidification. However, with the 2-stage units, they can run in low stage for longer periods of time, helping even temperatures and reduce humidity. In my opinion, if you're going for a higher end system with the Infinity controls, keep the Infinity outdoor units if they are a feasible option in your budget. It may be worth your while to get another estimate or two, if nothing else for comparison. I tend to recommend a more simple system myself, but your price for 2 Infinity systems installed is attractive, and for your location, I think you'd benefit from the 2-stage operation. I assume the dealer sized both units properly (that's step 1 to efficiency/comfort). The fact that they recommended an additional return is a good sign that they understand the need for adequate return air for these systems to work well.

That combo of condenser and heat pump is rated at 35,000 btu cooling (almost a full 3 tons), 12.95 EER, and 15 SEER. It is a Performance 15 Puron. Those are excellent EER and SEER numbers. As for the gas furnace, higher efficiency means less fuel waste and doesn't have anything to do with btus. I would question the big difference in the size of the gas furnace between the 2 choices (110k versus 80k is a huge difference). Your original post mentions 95k btus. These numbers are all over the place. Anybody do a heat gain/loss calc? There is a 15% savings in gas consumption between a 94% and 80% efficient furnace. The 94% does not qualify for the $150 Federal Tax Credit (must be 95%). The a/c system qualifies for a $300 Federal Tax Credit (15 SEER, 12.5 EER min) plus another $50 for the variable speed fan in the air handler. Best to you. Here is a link that might be useful: Federal Tax Credits