Yeah, mine was designed fairly well for the upstairs of the home. My particular problem was that the basement wasn't considered part of the house despite its being insulated from the garage. They didn't put any registers down there. Seems to be a trend down here in the south. Up north, the basement was always conditioned space even unfinished.
Get yourself a hygrometer ($30), and monitor the relative humidity in your home. Keep it between 40 and 60% if you can.
I second that advice. I have a digital. I will be getting another to put in the basement (which I do dehumidify).
Until recently, I was working as an electrician on million dollar homes up in the Highlands/Cashiers area. The contractors installed the crappiest, cheapest systems in those homes that I had ever seen. The rich saps paying for those fancy lake homes will be uncomfortable forever in them.
I saw one unit that was installed in an almost-inaccessible attic space above a bedroom. There was just no way that anybody was ever going to get up there and clean the coils or change the filter.
I've seen that kind of thing - put the air handler in a tight corner of a hot attic, or in the smallest closet they can get away with. I like mine right out in the open in the middle of the basement for easy access. As I finish the basement, I've made sure to leave a large space around the unit, and am installing a 72" opening with folding doors in front to allow easy access.
I have a walk-in attic, and when I install my unit, it will be hung from the roof rafters for noise isolation. I sized my own ductwork using a demo duct-design program I downloaded off the internet.
Right now, I am heating the entire 1300s.f. main floor with my Rumford fireplace. I am especially pleased with it's performance, since it is the first masonry fireplace I have ever built.
There are about two months in the summer here in WNC where the RH hovers at 95%. Two summers ago, all my furniture and my log walls started to get mold on them. So last summer I installed a 6000BTU window AC unit, which kept the RH at 60% the entire time.
By next summer I plan to have the central unit installed. I will buy the unit from these guys: airconditioningexchange.com, who sell quality units for less than half what your local contractor will charge you.
I also plan to install an Air-Bear filter, since we live on a dirt road and have a dust problem. The fireplace produces a fine ash that settles on everything, too.
But you know, you can't tell anybody anything. My neighbor built a two-story Deltech home (one of those round ones), with a huge amount of South facing glass. I told him (pleaded, actually) to install a zoned system; Otherwise his upper floor would be too hot and the lower floor would be too cold.
Well, he didn't listen and it's just as I predicted. The guest bedrooms upstairs run at 85 degrees when the downstairs is 65 degrees. His guests have to open the windows in the winter, and just suffer in the summer. His master bedroom is frigid at all times. Oh well...