are there dampers on the individual lines coming off the furnace that feed the rooms ?? if so, you should be able to close some of the basement level dampers say, 50% and the main floor ones about 30% to get more airflow upstairs.. if there are no dampers inline, you could install some. then you can more accurately control the amount of airflow throughout your house.
or the inline duct fans, but i prefer more control personally
i hope this helps