Need super quiet exhaust fan

Nsgarch's solution is clearly a better mousetrap. Outside of that, Wpines is right. Panasonic is the way to go. For a ceiling mounted fan, they are spooky quiet.

Thanks guys. I like Nsgarch solution.

Again, Nsgarch is correct.
Don't use a metal duct hose to avoid more vibration.
Try www.build.com to find silent fans

If you don't want to hear it, the fan *must* be remote from the room, with generously sized lined ductwork between the room and the fan, with at least one elbow. Use an aluminum or cast grille, not a cheap stamped steel one, at the room, and no damper (dampers generate noise). For 150 CFM I'd use at least a 12x8 duct...the lower the air velocity the less the noise.

For makeup air the transfer grilles, optionally with a filter between, are a reasonable choice. If the space from which the makeup air is coming is noisy, you will want lined ductwork with one or two elbows in it between the transfer grilles. A door undercut would have to be too large to transfer 150 CFM.

Essentialaudio's details/tips are all good ones. You shouldn't need balancing dampers** unless you are exhausting more than one area, or have more than one return grill; in which case balance is achieved by adjusting the size(s) of the different intake registers relative to one another.

** Most externally mounted fan units are supplied with backflow dampers which close when the fan is off (to prevent cold air from entering ;-)