I have a 17+ year old Bryant furnace and AC. The AC has limped through two summers and has to be replaced. The furnace is my question. It's 100k btu. It works just fine, but I am sure it's not very efficient. It has a poor filter and no humidifier. If I'm replacing the AC, would it be a good idea to replace the furnace along with it. If I do, I'm leaning toward something like Rheem's modulated system with a 14 SEER AC (best for my budget). Dual fuel costs to much. Replace both or keep my old Bryant? Thanks for your thoughts!!!