A little trick I have used for years is a 240 volt fan (like a small PC box fan) running at 120 volts so it is half speed and practically silent. If you need more airflow then this won't do it. I set it over the tubes on my preamp and with the perforated lid it pulls air through and out of the tube area.
This is all for naught once the A/C kicks on in my room and the airflow noise is annoying for several minutes. Win some. Lose some.
I always wanted to rig up a duct to the attic space to totally exhaust the hot air. But I don't have enough component heat to justify that fun project.