Since you haven't mention price as a consideration, I would recommend going for an old (1920's) Oscar Schmidt 12 with a long scale, either a Stella or a mahogany Sovereign. If it is really the sound you are after these babies have it. Heck, they created it. I have a Sov, and what is usually striking to others who play it is that, tuned down to about B, the two strings of each course do not sound like two strings, one low and one high, but more like one complex string. Of course, to play these wide, long fretboards, one needs a somewhat large hand, but with a good set-up, they are not hard to play after some getting used to.
Far more available, and somewhat less expensive, are the great replicas by Todd Cambio at Fraulini. I have only played one of his early tailpiece models, but that had quite a sound, very similar to the old Stellas I have played. I have spoken to Paul Geremia and others who own Fraulini 12s and they are very satisfied customers.
I would highly recommend getting a pin bridge as opposed to a tailpiece, as I think the stronger connection to, and tensioning of the top gives much better tone and volume. Personally, I like the 6 pin bridge. When restringing, I remove all strings so that I can get my hand inside and make sure each pair of string balls is correctly seated under its pin before stringing the head and tensioning.
I know that Mike Hauver is also making Oscar Schmidt replicas, but I have never heard or played one of his guitars. You can learn more about them thru Neil Harpe's stellaguitars.com site, where you're probably already headed.
All for now.
John C.