I purchased a Comfortmaker gas forced air furnace (CGUA Series) in 1989 and it was professionally installed. I've had minor problems on 2 occasions during that time, and both problems I was able to fix by purchasing an inexpensive, small part from the local heating and cooling parts supply house. It is reliable and cost effective. The issue of capacity (will it heat/cool your house) is a matter of the installer who figures your need and matches it with a system. Comfortmaker has systems big and small. Comfortmaker dealers (and the factory) have provided warranty help, so I would feel confident it is backed up. (My unit was out of warranty when the two small issues came up). Comfortmaker is big enough to be nationwide.