We have been happy with our Trane indoor Forced Air furnace with model # TUE100A948K2, except that the upstairs is never as cool as the downstairs, and when it finally gets cooler upstairs, the downstairs feels too cold. We are therefore thinking of upgrading the motor to push the cold air more quickly upstairs. Is this a good move? Which upgrade would you recommend? Any specific model of a motor you could recommend?