Does your keystoker not keep up with heat demands?
I was used to hearing and feeling the WA furnace fan as well. When I installed my boiler and air handler I originally thought there was no way that could work when it got cold outside. I can just about feel air coming out of my vents from the blower, it's that slow and quiet.
It's a balmy 8°F out this morning and steady 72°F here with my coffee. Even at well below 0°F we've never been without sufficient heat and my house is not an energy rated home either. The nice thing about slow air movement is some of the dust is cut down and like heating with a stove, everything around you gets warm rather than just a blast of hot air for a minute or two then a draft.
Just wanted to throw my $.02 in. May not be of value to you but sometimes a different opinion can alter our thoughts just enough to have a eureka moment.