I've got the 743 (around 40$) and it was originally too loud to use while you try and sleep (only time we use them)I had to put a variable speed controller on it to limit it to 3/4 speed also the on/ off button broke as I think its a bit of a poor design and its right on the middle of the fan, great fan but this was my experience with this model.
next time I would look at one with different speeds