Yes we did a manual J and a manual D and yes the capacities and ductwork seem to be up to scratch (with some minor duct adjustment in the basement). The house is an old (at least 40 years old) 3700sqft ranch in St. Louis with a gigantic great room with a vaulted ceiling as the main part of the house. The bedrooms are actually reminiscent of a 70's ranch-style house.

The 5-ton system will service the great room/kitchen den (which is the bulk of the square footage) and the 3-ton will service the bedrooms.

Here's the quote - it doesn't seem all that ridiculous to me but would be interested in what you all think.

System 1:

4TWX5060 (5 ton X15i)
TUD2C100A9V5 80% 100kbtu VS furnace)
4TXCC060 Coil
$8800

System 2
4TWX5036 (3 ton X15i)
TUD2B080A9V3 (80% 80kbtu VS furnace)
4TXCB036 coil
$7300

The whole system comes out to around 16k, to include honeywell visionpro IAQ tstats and I think 4" or 5" media filters. Installer swears current lineset is sufficient. so no new lineset or electrical work needed. I think I can get around 1200 in rebates for this system (16.5 SEER) which would bring the cost don to more like 14k.

Where did you get those model #'s? Off of a quote?

The 5 ton system should be more like twx5061 and even at that none of those matches comes anywhere close to 16.5 SEER. Match up is not good one. You can use the ahri directory to find much better one. 3 ton system is a match up that is more around 14 SEER.
The 5 ton quote you give uses 21" wide cabinet furnace and coil. The 24" wide cabinets work much better for SEER ratings. Is there a space constraint problem?

Price is not out of the ballpark but since 5 ton system is not good match up it is not a good deal in my opinion.

Definitely, I would want the 5 ton HP to have two stages.

Just curious, why the 80% eff two stage furnaces? I may know why. Would like to hear from you.

All quality equipment. Pricing reasonable with the HW VP IAQ and media
filter cabinets. If interested, I think on the HW stat, a WiFi version with app is available. Might be worthwhile to look into.

Still alot of BTU firepower both cooling and heating. You want to be sized correctly. You have a load calc in writing on the software letterhead and
have reviewed carefully for accuracy and good design temps for your location both inside and out, cooling and heating?

IMO

Yes I got the model numbers from a quote. I'm bummed to hear they are not a good match. That's why I love gardenweb though.

I do not understand how to use the AHRI directory.

Tigerdunes - I'm replacing a 5/3 split. 80% furnance because the install of a 90% (particularly the pvc vent) is problematic in this location, and if I'm going dual-fuel heat pump then I shouldn't be using the furnace that much anyway, right?

I have a load calc on a different company's letterhead (last year). Cooling capacity is accurate, heating is a bit of overkill on the 3-ton side but I think that's because the furnace is being sized to the AC not the load.

Reviewing the audit results from last year I think I will get more mileage improving insulation and sealing duct work than buying fancy equipment - it might even let me downsize from a 5-ton to a 4-ton. If you send me an email address I could share the energy audit if you want to see the numbers.

Half of the house is over a concrete-lined crawspace. Trying to decide if it's worth spending ~$1500 to have it sealed. Humidity (especially in the basement) has been a problem this summer. so I'm thinking the answer may be "yes" but I don't have infinite money to spend on this...

I get the regular tube and aluminum fins carrier or goodman.
I can get almost equivalent units for around 12K after rebate.
Check my quote under thread Infinity owner feedback below.

" I can get almost equivalent units for around 12K
after rebate.
Check my quote under thread Infinity owner feedback below. "

His quote is for straight AC with gas heat. yours is for a dual fuel system... Dual fuel systems are more expensive as well as you have a 5 ton system.
Is dual fuel what you wanted?