Not wanting to tear into the roof like I did with the Fantastic Fan or the one you pictured I chose to put a
VORTEX fan in the bathroom,It is a snap to do with very detailed instructions and it is multi speed and reversible.
Here is an earlier post that is really helpful.
As long as you are replacing the vent covers it is a good idea to replace the
seal on the edge of the vent,they dry out and new ones will give a tight seal with the new vent cover.