I'm in the midst of finishing the designs for the systems for my new place, and we're using fujitsu ducted split systems (Fran originally spec'd Mitsubishis, but the mechanical subcon wanted to go with fujitsus and it seems like they're fairly interchangeable in terms of noise and other specs.)
I believe that the idea with these is you get the best of all worlds - they're mini split systems - relatively small, efficient, and affordable - with the condensers placed outdoors, but you can also place the air handler unit outside of the room being treated and run appropriate ductwork to reduce noise further. With a well-implemented system, it should be very quiet. At least that's how I understand it. Not sure if this would be an option for what William has in mind, but just throwing it out there. Of course, my system has yet to be built, so I can't personally comment on its noise level. But Fran claims that he's had good luck with similar systems in other builds.