If you aren't burning any harder after you put your plenum / collector / manifold on, then you are not washing enough the heat off your stove. The heat will just radiate off your manifold, I bet if you put a laser temp or stick a stack temp gauge you’d see it was super hot. My collector doesn’t usually go over 150 f, unless my fans are off.
I think you should stick with forcing your air with your two registers like WNY did with his stoker in his basement. You’ll heat your house nice with 140 degree air blowing out with a good 8 inch booster or two. There isn’t much natural current in your basement, and you’ll lose a lot of heat out of your basement walls.
Just feeling the air is not a good way to test it, 80 degree air keeps my house warm when it’s in the 50s outside… and it feels cold to the touch. You should go to a home improvement store that sells digital indoor/outdoor (with temp probe on a long wire) thermometers. Experiment with it and see where the air is hot. Keep it at your register and then you can see how much hot air the needs to be for you to be warm in your house. If it’s at your register you can get a feel how hard you have to burn. This is a bad time to start figuring this stuff out, so don’t get frustrated.
Don’t be afraid to burn that thing at maxxed out at 90,000 BTUs when it’s super cold. I looked at my tracking paper today. To keep my house warm during those cold -1 windy (-25 wind chill days late last week), I burnt 152 lbs. That’s 6.333 lb / hr. If it was 160lb that would be 2,000,000 btu or 83,333 BTU/hr at 100% efficiently(60-70% for me) if my coal is 80/lb per 1,000,000. Personally my old stove will heat up to over 700 degrees on the cast on my stove. (yeah I overburn, I need to start a discussion on safe overburning.. because I’m not sure how much is too much).