Chris White is the designer. His designs have been built in a number of locations. Most of the recent Atlantic Series cats have been built at a plant in South Africa. I have seen a few of these only on the exterior in various anchorages -- but what I saw was impressive.
However, the most recent A57 (a slightly stretched version of the A55) was built at Aquidneck Custom Boats in Bristol, RI. I have only seen of this boat what is posted at Chris' website (http://www.chriswhitedesigns.com/atlantic57/index.php)
, so cannot comment except to say that the design, layout, and performance reports are impressive. I would expect the quality to be well above the typical production catamaran.
Note on the Atlantic-series catamarans, that the cockpit is forward of the main salon. I think this is a highly desirable feature if you plan to sail rather than motor cruise. I have been aboard most of the major production catamarans at the boat shows and find with rare exception that the steering and sail trimming arrangements verge on ridiculous.
If you need more info, you can call or e-mail Chris White directly. He is a great resource on mulithulls and is generous with his knowledge, which is a good thing because you have now exhausted mine.