Goodman is ok, they had made some pretty bad equip in
the past, but newer one is ok.

You need to know BTU of your existing system to compare

Goodman GMS8/GDS8 ~$500 (80% SS/MS).
Goodman GMS9/GCS9 ~$700 (93% SS/MS)
Goodman GMV9/GCV9 ~$1100 (93% TS/VS)

I bet they are offering GMS8s or at most 9s. Think of that
as $500 - 700 discount on $4500 install. Not bad
but not sooo hot either.

Find good trusted installer.... Mention 4500 offer.