I didn't read you whole post because,,,,,,,,,,,,,,,ahh what the hell, it was just to darn long for a forum question! I did read far enough though to where it said the house practically lacks any appreciable insulation. Don't waste any of your money on a decent mechanical system until you update the building envelope. I doesn't make any difference how efficient a system you have, if the heat is coming into and going out of poorly fitting windows, doors and non insulated walls etc. you'll be wasting tons of money. Just by doing those things first you'll see a savings. Then you can upgrade the mechanical systems. Oh, one more thing, the foam insulation betweem the roof rafters is a big no no. Thats not how its done. Moisture will get trapped between the roof sheathing and the foam and eventually rot your roof. Your next roof job on the house might be a total tear off. And by total I mean replacing some of the wood below everything. It happened in the house I bought 15 years ago. Fortunately I was aware of it and the seller dropped one giant you know what when I poked my screw driver up through his soggy roof. I'd suggest you rearrange your priorities. Just curious, are you a journalist or something like that?

Welcome back April. I am glad to see you have done some more homework. I own Carrier Infinity equipment, so I know it will keep you comfortable in the cold Michigan winters. I have heard mixed opinions about Lennox, but I have no direct experience. I am going assume Contractor #3 is a competent installer and he has sized your equipment properly. I am glad to see he is offering the Carrier rebates. Here are my comments for the Contractor #3 options: Furnaces: Option 1: I would not recommend an 80% AFUE furnace for your winters. Option 2: This is the two-stage Infinity furnace. It is a good furace and will work with the Infinity controller. Option 3: For $300 more you get a three-stage furnace. This would be my recommendation with the Infinity controller. Air Conditioning: Option 1: This is a single stage compressor. I think 4 tons is oversized for your climate. Option 2: This is the two-stage compressor. This is the AC to get if you have humid summers. This AC will work with the Infinity controller. I believe this AC with the 58MVC furnace will qualify for the $1000 Carrier rebate. Option 3: This AC in my opinion is over kill for your climate. It is not worth the money. Ask contractor #3 how much a 10 Carrier labor warranty would cost. You should consider getting this warranty for peace of mind for the next 10 years. I would also want to upgrade to a 4 inch media filter. This should not be a costly upgrade assuming you have to room to fit it. You should also qualify for the $500 tax credit if you haven't already used it.

I agree with Mr Salesman that a heat pump is the way to go. I'm not even sure why you have gas heat in Florida. Electric back-up strips can be used in the air handler, or you can have a gas furnace in the air handler as supplimental heat. Below 32 degrees F outside air, a house loses heat faster than the heat pump can supply it, so supplimental heat is needed. What are your electric costs ($ per kw-hr). The 2TTX5042 condenser with 2TEE3F40 is a matched set rated at 42,500 btu-hr, 12.8 EER, and 15 SEER. These are fantastic numbers. Your true cost of operation is determined by EER and not SEER, much to the surprise of many people. EER is rated at 95 degrees outside air temps while SEER is rated at only 82 degrees outside air temps. That air handler does have a variable speed blower. The 2TTX5042 condenser with a 2TXCC049 air handler and UD080R9V furnace is also a matched set rated at 40,500 btu-hour, 15.25 SEER, and 12.8 EER. Not sure if the blower is variable speed. You may be able to check Trane's website for that info - search on the furnace model#. There are no HSPF ratings since the above systems are not heat pumps. For your piece of mind, you should consider a PARTS AND LABOR warranty. The manufacturer's warranty is parts-only, no labor. You can search www.energystar.gov to find the rebate requirements. You'll have to step up to the XL16i with the right air handler to get the required SEER/EER/HSPF. All 3 must be met to get the rebate. The 16i uses a 2-stage compressor. Typically these systems are much more $$ to purchase than single stage compressors. The VisionPro is loved by the pros. The VisionPro IAQ is even more advanced. You can check them out on Honeywell's website. You ask solid questions. An HVAC-educated homeowner (myself included) helps to insure a good purchase, a good install, and a happy ending. Best to you. Here is a link that might be useful: ARI Directory

“My understanding is that these promotions are typically in fall/spring and might disappear in 30 days. Since a commitment to HVAC vendor needs to be made about when framing happens, but the actual equipment might not be installed until many months later, how does this work?” It should be noted the installation usually has to be completed within 2-weeks of the promotion’s ending (Carrier). Respect these dates or you might be left out in the ‘cold’ with no rebate! Tiger is right - new homes do not qualify! SR