Hey folks, I need to install a 3 ton and 2.5 ton furnace in my attic. I have had 4 different companies come out and give me estimates and 2 say to go with variable speed and the other 2 say that the units are too small to get the benefits of variable speed units. I live in Houston with a humid environment. The extra cost of variable speed over single speed is roughly $750.00/unit. Any thoughts on this?