Product upgrades

Looking to upgrade your old heater? Look here for information on which product is the best like-for-like replacement.
What would be a good replacement for a Reznor UESA 102? What would be a good replacement for a Reznor UESA 83? What would be a good replacement for a Reznor HEA 105? What would be a good replacement for a Reznor HEA 79? What would be a good replacement for a Reznor EURO H 30107 S? What would be a good replacement for a Reznor EURO H 30087 S? What would be a good replacement for a Benson ULSA 100? What would be a good replacement for a Reznor UESA 55? What would be a good replacement for a Reznor HEA 66? What would be a good replacement for a Benson ULSA 075? What would be a good replacement for a Reznor EURO H 30067 S? What would be a good replacement for a Benson ULSA 050? What would be a good replacement for a Reznor ECOO 5050B? What would be a good replacement for a Benson ULSA 035? What would be a good replacement for a Reznor ECCO 5033B? What would be a good replacement for a Reznor UESA 35? What would be a good replacement for a Reznor ULSA 100 EC? What would be a good replacement for a Benson ULSA 025? What would be a good replacement for a Reznor ULSA 100? What would be a good replacement for a Reznor ULSA 075 EC? What would be a good replacement for a Reznor ULSA 075? What would be a good replacement for a Reznor ULSA 050 EC? What would be a good replacement for a Reznor ULSA 050? What would be a good replacement for a Reznor ULSA 035? What would be a good replacement for a Reznor ULSA 035 EC? What would be a good replacement for a Reznor ULSA 025 EC? What would be a good replacement for a Reznor ULSA 025? What would be a good replacement for a Reznor UPA 70? What would be a good replacement for a Reznor UDSA 073-4E? What would be a good replacement for a Reznor UDSA 073-2?