I had a Lennox 2 stage furnace installed recently(G61) and am considering replacing an 8 year old AC unit( Bryant 10 seer). I am considering replacing it with a compatible Lennox unit but do not quite understand the advantages of a 2 stage unit or if it is worth the additional cost. The sales person did a load calculation and I need a 3 ton unit. I live in Atlanta with hot, humid summers. Thanks for your advice.