Most of the good products today are energy star rates. Trane is among the better brands. Your best bet is find a Trane dealer. I believe that The Home Depot even sells Trane Products. 4 ton is a little small for the application. If you were to increase the capacity, with the new energy technology, you will still save on that electric bill. FYI, the evaporator/exchanger (in the attic) should also be checked and probably replaced to match the compressor unit. It will not be a cgeap job but in the long run, the savings and better coooling will be worth upgrading.