Trane XL16c. I am about to pull the trigger on this or the AS equivilant but am still confused on Tstat. This is a hybrid unit with 4 stage heat and 2 stage cooling. My confusion comes in where one vendor recommends an 800 series tstat which can range from 1 stage to 3 stage control where as another recommends the 900 series which has 4 stage control. NOTE: both of these are AS/Trane products. My question is what is the proper/best Tstat to use with this unit?