Hi all. I am replacing an old gravity furnace in my 2000 square foot home in LA. I plan to replace it with a high efficiency gas furnace. The old unit has asbestos and I have someone to remove it safely. My questions relate to different suggestions from different installers.

Regarding ducts and returns.

One company suggested cutting new heating vents in floors throughout the rooms and using the existing old vents for returns plus another large return. Said this is the best route for quiet and if I decide to add A/C someday.

Another company said I could use one large return only and cut in new vents.

Finally one suggested one large return and use the existing vents to deliver heated air. That seems like the most reasonable, least destructive and probably least expensive route.

What would I want to consider in terms of functionality, noise, efficiency?

Other questions are about 2 stage or variable blowers, put coil in now for later A/C addition, and sizing the furnace.

Help with any and all would be great as it is getting a little chilly here with no heat.

Thanks

Walter G