You need to continue looking for a good HVAC contractor. Ideally you will find a contractor who will do his own load calculations to confirm the sizes. Don't let these guys sell you over sized equipment.

No way should the bid be the same for smaller equipment.

Do your own Free Whole House Load calc
From what you describe a 1.5-Ton or 2-Ton A/C should do the job; & a 40,000 or 60,000 95% furnace should handle the heating.

Make sure the duct system is properly sealed with plenty of airflow... and ducts well insulated if not in conditioned area.

Here is a link that might be useful: Free Whole House Load calc

No way should the bid be the same for smaller equipment.

Do your own Free Whole House Load calc
From what you describe a 1.5-Ton or 2-Ton A/C should do the job; & a 40,000 or 60,000 95% furnace should handle the heating.

Make sure the duct system is properly sealed with plenty of airflow... and ducts well insulated if not in conditioned area.

Here is a link that might be useful: Free Whole House Load calc