Since the success of the downstairs 3 ton unit, I am looking at replacing my upstairs conventional with a geo. The current unit is a 2 ton trane and has died a slow painful death from 16 years of service. ( Long Story). My question is the advantages or issues to consider with the pumps built in or external. Units on the radar: Climatemaster Tran 22, which has a internal pump Coldflow CFX24, which requires a external pump MiamiHP HPX24, external pump All would be 2 stage. I like having the external pump to purge the lines, but once that is done, the internal would be variable saving some $ over time. DIY install, Ive enjoyed the journey and learning, I appreciate any feedback. Loop field is already in, 2x800 ft loops buried 7ft+.