I can't think of any off hand, but pay a visit to the Linkwitz Lab website and read up on the Phoenix and Orion. Not in your price range, but they're both open baffle and there's plenty of good reading there. You might take an interest in the Pluto. If you want to stretch your budget evil, they can be built for $600-$700. Keep in mind that this includes the built-in amplifiers for them. Oh, and I almost forgot to mention Troels Gravesen. Google him and read through his website. I don't remember if he has an open baffle project, but you'll find a whole lot of interesting projects. I don't need another pair of speakers, but the Poor Man's Strad has been tempting me for awhile.