I just replaced the noisy three speed fan in the living area of our Lexi with a Maxxair Maxxfan Delux, 10 speed. So happy with it that wife gave the OK to replace the crank up vent in bedroom with another Maxxair. Up to speed 5, you don't really notice it's on. On high speed, #10, it no noiser than the old three speed on high, but it flows so much more air. It's reversable and it works great. Thinking of having the rear draw air in and the front draw air out.
Took the old 3 speed fan and replaced the little bathroom fan with it. Yeah, that little bathroom fan is very loud for it's small size.
Cheapest place I found was Amazon, around $300 bucks shipped.