I am in the process of gathering together quotes to have my AC units replaced. I would like to switch to Heat Pumps and use my existing gas furnaces as backup and I would also like to meet the requirements for the new IRS rebate. Three of the four quotes state that with a 15 SEER Heat Pump and proper coil, I can meet the specs needed to obtain the rebate ( using Carrier or Trane units ). The Tempstar installer says that there is no way to meet the specs of 15 SEER and 8.5 HSPF unless I replace my furnaces with variable speed units. Who is correct ?