I currently have two 3 ton 24 year old amana systems that I desperately need to change out. They are 8 SEER systems and I live in the deep south where the humidity is very high. I have received several quotes. I am looking at the Lennox 15 SEER xc15 with the G60v Furnace, Lennox 19 SEER XC21 with the same furnace, and the Maytag 23 SEER with IQ Drive. The cost on any of the systems are very high considering I have to purchase two for my home. I plan on living at my home for a long time so I need to see which system would be the most cost effective. Can anyone give me a formula to show me how much savings I may possibly receive for the SEER ratings or does anyone have an opinion on which system they feel would be the most reliable over the long haul?