Wow 6.5 sones is pretty loud. If you want something real quiet, the
panasonic line of fans are real good. 1.2 sones in some cases. You
wont even realize its on!
Check out

http://www.panasonic.com/consumer_el...tilation_fans/

The ultimate in quiet is an inline fan. All you have in the room is a
vent in the
ceiling that goes to the fan motor and from there out of the home.
Inline fans can be a problem though if you dont have attic space right
above the
area.

I am installing the inline fan in my upstairs bath and already have one
of the smaller units in my basement bathroom.

Price can be high for them locally. I ordered mine from either ebay
(new)
or just did a few searches for the model that you want in google.

Tom