I have a 25 year old BDP 517EN air handler with a hot water coil mounted above it. It is a multi-stage system. There is a circulating pump coming off the line from the water heater to supply the water and circulate it. With my system being 25 years old would it be smart to replace the water coil with a new unit? Would that help the efficiency? It seems as though the warmth of the air from the vents has deteriorated in the last year or so. Just trying to educate myself on this system before the contractor comes out to look at it. Thanks for any advice.