Air handlers and furnaces aren't usually found side by side in Naples. If you use a furnace, you probably shouldn’t need to consider an air handler.
Air handlers are usually paired with heat pumps and deliver airflow throughout your residence. Some models also have secondary heating and cooling pieces to assist the heat pump.
A furnace works in a different way by sending hot air into your vents, which send it across your house. As furnaces have combustion chambers to make warmth, they don't have some of the pieces you'll spot in a standard air handler.