Hello, 15 year old home in Az. Downstairs about 900 sq. ft on mini splits. Up stairs furnace and coil in much needed closet that I would like to make into powder room. Current system 12 seer 4 ton compressor with 88btu furnace. Would like to move above current location to free up the space or put in the garage and run a return an supply from the floor below to the attic. I have received 3 quotes. Two of them for Rheem units and one for goodman. These were 18seer. My questions are if 18 seer is 18 seer and the install is 90% of a new system install, why not go with the least expensive ? and would it be too draining on a system to put in on the floor below the one it is cooling and to the attic(about 15-20 ft)
thank you.