3 "free" quotes means a lot of running around for "free" to get one job. Some homeowners go to 5-6 free quotes. That means I run 6 quotes for 1 job which has to carry the cost of the 5 other quotes. What appears free must be paid by someone, and that someone is you. (How much of your money you want spent doing design and specification for 5 other people, because that cost is part of what you are paying!)
So design and specification suffers because you can't do ekg, xray, and mri for free, so everyone makes little better than WAG.
Once the job is one they don't say, "oh, we simply guessed before, figuring we wouldn't get the job. We oversized by 17,000 btu, this duct will never handle 1400cfm."
No, that's not what happens. Once the die is cast they gotta keep rolling or they'll never survive. The equipment on the contract is getting installed no matter what duct is discovered. It's a race to the bottom. This is survival. The energy bill, and if the equipment works well, are not the concern. Getting the job done as quickly and cheaply as possible, and having the stuff WORK is the concern.
Wait until you see what your ESP is. I'm thinking you'll be then , then hopefully thank your lucky stars you took the opportunity to do it right.
The energy bill will be the true tell. A year from now share your savings.