There is a lot more to a proper install.
Is the contractor doing the install using the proper parts as recommended by the mfg of the equipment?
Are they making sure the ductwork is correct and not leaking anywhere or just ignoring it? Are they making sure the system is balanced, or are they just "throwing in" a new system?
Is the wiring being done neat and orderly, or are there wires hanging out everywhere? Are they checking their work or just installing the stuff and running off without checking how the system works?
It all comes together no matter what level system you buy, an bad install will not give you as efficient a system as a good installation will.

there are three equally important components-quality HVAC, the install by dealer, and probably the most overlooked and disregarded is the ductwork system.

IMO

Huge DIDO, well said dualref.

Here is a link that might be useful: Barron Green Team

Just like many professions today including HVAC, there is the lost art and/or emphasis of craftsmanship and the rush by many dealer's installers to get in and get out.

IMO