Ok, here is the scenario....We live in Fort Worth, TX where we experience some temperature extremes. Our home is 3900 sq. ft., two story, built in '99. We currently have two Carrier units...one for downstairs, one for upstairs. We are ready to upgrade to more efficient units and need some input as to what manufacturers we need to consider. I have found, reading various threads, that the install is of utmost importance, but for our area/scenario, would you help us 'narrow the field'? In the winter, the current system requires that we throw on the heat strips if the outside temps dip below 30 which really sends the electric meter smoking! Is this something that we should expect with any heat pump? One other factor that needs to be considered is that we will be selling this home in approximately 3-5 yrs. Thanks in advance!