Dang you guys have some big thumbs! When I first started this full time a few years ago the rot was 600sqft for older home and 800sqft for newer energy star homes. But with manual J I have done new custom homes with as much windows than wall area and have to install 600 or less per ton, with multiple or zoned systems on one floor because heat gain was so much higher at one end of house the duct system was crazy or temp differance was to high. At the same time I get an older home with more infiltration but 1 small window per bedroom and low ceilings and almost square so minimal parameter that calls for closer to 800. But even with out wrightsoft 100k btu heat and 4 Ton cooling is way to much. As was said, a warning is when you have to pay for the equipment for the contractor up front!