I think the two biggest importers are Uberti and Pedersoli. There is also Pietta and Amadi.All from Italy. Theyall make a quality firearm. I have a Mitchell Arms SAA (made and imported from Uberti)in .45 colt and haven't experienced a problem.
http://www.uberti.com/firearms/1860Army.tpl
http://www.davide-pedersoli.com/
http://www.pietta.it/index_2.htm

I'm not sure if Pedersoli makes a Navy revolver, though, so it may be from Uberti.
Couldn't find a site for Amadi, but here is the link for the Navy Arms site where they mention who their vendors are.
http://www.navyarms.com/html/about_us.html