I'm with Kendall - the best is Apollo, and one of the smaller ones would be in your price range.These are built by Nick Apollonio from Rockport, Maine (and if you're lucky enough to find the odd used around, it'll probably be known by his name). Nick has found ways to do things with bracing that allow more sound out of a 12 than you ever would have thought possible. Gordon Bok plays Nick's 12-strings, as does Judy Collins and Paul Stookey. I love mine with a passion - and I think Kendall has one too.
The website is www.members.mint.net/memusic. (Sorry I don't know how to make the link light up blue.)
Seriously, if you're buying a 12 string, you couldn't find a better instrument or (for that matter) a better value. I think they're the best in the world.
Good luck!
Dan (who _still_ needs to reset his cookie....)