Thanks to hcong, RyanHughes, tedkidd and motoguy128 for your comments and recommendations. I've decided on the Carrier Performance 25HCB636 outdoor unit and the FV4CNB005T variable speed fan coil. The Carrier Performance components are priced at the top of my budget while the Infinity components are just more than I want to spend at this point.
I asked each of the 4 contractors that has given me an estimate about a whole house humidifier. Several included a by-pass humidifier and a steam type in their estimate. The contractor I am leaning toward didn't include the steam type, just the Carrier HUMCCLBP2417 by-pass type. When I asked him about the steam type. He replied that he doesn't like them because "they don't hold up, we have had problems with every brand of steam humidifier plus they need a lot of maintenance." Is a by-pass type a better choice? The steam types are all twice the cost or more than the by-pass units. Everything I have read indicates that a steam type humidifier is more efficient and doesn't waste water like a by-pass unit does. What do you guys think about them? Do you think they are worth the cost and possible trouble? Any experience, good or bad? Would you stay away from a steam unit?
I also asked that same contractor about an additional housing for disposable filters. He said "if you're talking about a media filter they are very restrictive to air flow and can reduce air flow." I guess he recommends just using the filter that comes with the unit. Are the larger 4" filters a bad idea? My current duct work configuration includes a 24" x 8" drop from the main return trunk line that runs parallel to the fan coil and turns 90 degrees and terminates directly under the fan coil housing. That enables the return air to enter the fan coil from the bottom and not through the side. I think one of the contractors said that the bottom or underneath entrance is better. Would an additional filter housing fit in my current configuration and be desirable? Maybe it would be installed between the horizontal part of the return and the bottom of the fan coil housing? In that configuration the fan coil housing would sit directly on top of the additional filter housing.