My A/C went balls up last year I decided to replace it and my 16 year old furnace in a package deal. Ended up going with similar efficiency A/C we don't run it much and it worked just fine. But my furnace I upgraded to one of the super efficient models with stronger fan. We keep the fan going all day to keep the air circulating. I really noticed the amount of dust that accumulates has gone way down (three dogs, lots of dander). Rooms are more evenly warmed/cooled. Better filters keep the furnace cleaner as well. Cost's less to heat and cool than the original equipment put in by the home builder. Carrier furnace is what we went with. Between that and replacing my windows it has proven to be much more comfortable in the summer and winter.