I have forced air HVAC in the basement. The dampers (in the louvers) in the basement are closed all the way, and theres still a fair amount of air leaking out... perhaps 100 cfm x3.
The main level has the dampers mostly closed. I get about 70cfm x6.
The upstairs are wide open. Perhaps 5cfm x3. Barely noticeable. Doesn't matter what the rest of the dampers are set to.

Upstairs are fed via 4" pipes from the main duct. The main duct runs the length of the basement; the basement 3 are directly on the duct.

I need better service upstairs. Do I need to get better louvers downstairs? If so, any recommendations?
Increasing the size of the feed pipes is an infeasibility big project.
I've seen accelerators on the market... fans that fit inside the 3" feed pipe. Do they work? Are they too loud for a bedroom? It could be a significant project to run signal/relay cable up to the top floor...