I owned BW 600 series years ago, and don't recall which are the 685 equivalents. If they are the 2 way monitor types, I'd go with the 805N's if it were me and I wanted to buy BW. But that's past your budget, albeit worth the extra couple hundred bucks.
Otherwise I'd go with some 2 ways from Silverline Totem, or maybe NHT. ACI too has a few which are well regarded and look very good. I feel my SR 15 Silverlines are better sounding than the 600 series BW. About $600 $700 used.
I also saw a note about Audio 123 (?) in Tone audio magazines best products of 2008 which pointed to a floor standing pair for $699 THEY FELT WERE A GREAT VALUE. Check out the notes in their online mag "products of the year" category.
Good luck.