ur choices will be limited somewhat with efficiency because u r in a condo.if ur existing furnace vents to a main vent that is metal,or to a chimney,,you will have to get an 80% eff furnace,which is probably higher than what u have now.if ur furnace vents with pvc plastic,then its a 90%+ furnace & will need to be replaced with the same type...as far as central ac,,i assume its tied into ur furnace,meaning the furnace blower blows the cold air in the summer too..so u will be replacing the furnace,ac a-coil,and ac outdoor unit..because u live in a condo,i assume u can hear the furnace when it or the central ac is on??if so,consider getting a 2 stage furnace with a 2 speed air conditioner.they will run on low speed most of the time,greatly reducing noise from the blower,burners,and inducer.you would be surprised how noisy the new single stage furnaces are,can be a big dissapointment for those who is furnace is near the living room,etc.a 2 stage furnace with a single speed ac is also an option,,i dont know if ur ac unit is in the wall or sits on a balcony,or ground..the type & brand of ac somewhat depends on its location.most major brands r good but i would lean toward carrier/bryant right now,esp for 2 speed units..they offer very good warrenties,,sometimes 10 years on all parts,and 5 or more years on labor.get the best warrenty u can,,newer units will be very expensive to fix once out of warrenty,,they all break sooner or later.. i would est about $4500-$6500 for complete system,heat & ac..including installation,depending on what u decide on....dan