I installed MaxxAir's as well. In the bathroom just a cover as it already had a cheap fan. For the one in the living area I put in a TurboMaxx. That Turbo moves the air - I'd guess it changes the air in our trailer ever couple of minutes on high - never use anything but low. The point being, you could use that to ventilate out your trailer in no time flat. Here's a link to the one I got, but there are others: http://www.maxxair.com/turbo-maxx.html
One last thing I like about the TurboMaxx is that on the low setting it draws just over 1amp and still manages to move a lot of air. As be boondock a fair amount, the less power drawn, the better
Oh, and RVHiker is right - they really are an easy install. For the turbo I was lucky and found DC wires right next to the vent hole, so no need to run any new wire!