Jeez, Drew, you are way beyond my budget and what I can afford. Those of us that do this on a shoestring budget don't exactly have a choice.
My darkroom is a corner of our unfinished basement, so not a separate room. It is a combined space for wood working, fixing things, laundry, storage, and also where my furnace and water heater are located.
Funny thing is, in most 16x20 prints from 35mm I rarely have more than a handful dust spots. That's 16x enlargement roughly.
Good enough for me. I don't have any hepa filters or special smocks, and vacuum once every six months. If I came into some extra cash I would make it warmer there. In the winter the room is about 45 degrees.
You are far from the norm, Drew. You are one of the lucky few.