When you say you had 1 of the 3 condensers replaced are you speaking of an outdoor unit? If so, was the tonage to small? I'm not sure what you mean. As far as your room temp. varying from room to room. It sounds like a design problem. Your duct-work may not be sized properly. To big or to small. Rule of thumb is for every 700 sq feet you need approx. 1 ton of cooling (12,000 btu) a 5 ton unit would likely be what you need. Remember this is rule of thumb. Educated guess. For a house this size I could not imagine needing 3 systems to heat and cool it. If you had pictures of the duct lay out and Mod#'s of your equipment. I may be able to give you some kind of direction.