OK, let me defend myself (and thank you, your advice is good and I seriously
am learning more on these ng's than from all FIVE quotes I had, and I've
went with at least 3 very reputable long-time companies in the city)

1 - Cross posting is supposed to be poor etiquette. I came to this group
because I was told to by the HVAC group right off the bat not a place a
homeowner post asking questions to that group. So I posted to this group,
where that person told me to go.
However, someone was nice enough to reply on the HVAC group and told me
without seeing the job he just couldn't answer some of the questions. Fair
enough. So, I thought I could try and give details here, but without seeing
the job, I was just likely filling just up space on the ng with useless info
that wouldn't be helpful and also wasn't sure what sort of audience is on
this group. I honestly thought this might be just a bunch of other
homeowners with lots of personal war stories and not professionals who could
help me. Who knew? I misjudged. So I made my question here short and
simple.

2- We live between near Rochester NY. We have long, snowy winters and the
average humidity all year long is above 50-60%. Average low temps in Jan is
in the mid teens, Average high temps in July-Aug is in the high 70's to low
80's. Average morning humidity in the summer is around 88%.
The heat and humidity is a real health problem for my child who has a
serious medical condition and ends up in the hospital because of this
problem frequently.

3- I need to have this job done quickly. I've been getting quotes for a
couple weeks. I've check the Better Business Bureau site for any info on
these guys (all are in good standing), no one I ask seems to know anyone in
the HVAC business...everyone I know used the big businesses for their HVAC
and those are two for the quotes I got; all I can do is take the references
of the independent guys (and are they going to give me bad ones?).

4- They all told me the furnace I have to way too big, and they are all
downsizing me more appropriately. The only difference is in sizes is the
last quote we had from the Carrier fellow who wants to go with a bigger AC
(3 ton 10 SEER and the others all are saying a 2.5 ton 12 SEER).
And for that person who asked, the Carrier furnace booklet says variable
speed, nothing about 2 speed.

5- I am the type of person who usually researches everything to death before
I do something. I just can't with this. That's why I'm turning to the
generosity and helpfulness of you good folks in hopes I can get some
guidance here. As I said, I need to make a fast decision on this and I just
don't have time to research it. Without any feedback, I'm just going to
have to pick one anyway, so there's no harm in asking for a few opinions,
right?

I do appreciate your help and advice.