My house is approximately 1600 square feet (1950s split-level house with cathedral ceiling for the middle and top floor). My 19,000 BTU Friedrich wall unit just died (perfect timing!). I'm having trouble picking out a new unit with all of the choices (there is no exact retrofit). I'm wondering if it's advantageous to go with a higher BTU unit - I found a 25K BTU Frigidaire unit. Is there a possibility that it could cool the upper level without freezing us out of the middle level, keeping in mind that the ceiling of the middle level is also the ceiling of the top level? The house is open concept.