[dad911]

Do you have enough attic ventilation as it is now?
For $3-400 you could add considerable ventilation, and not use any power. Hot air rises. Add ridge vent, or mushroom vents near the peak, to let the hot air out, and more soffit vent ventilation at the eaves to let cool air in.

You still need to add ventilation if you add a powered fan. Have to draw in fresh air to replace the air drawn out by that 1200 cfm fan, or you will not really be getting rated cfm of airflow.