I live in a condo complex and have an Apollo 5010 gas hot water heater which acts in combination with a MagicAire foreced air system. This combination system is 8 years old. I'm trying to anticipate the future in that I expect the gas water heater and/or the foreced air system to begin failing soon. Other condo owners have said that they have had problems trying to replace the Apollo 5010 gas water heater. They say that this Apollo is hard to find and that the parts for it are extemely expensive. So, my question is can I replace the Apollo with a different brand gas hot water heater that acts in combination with my forced air system?