Some of the best imaging I've heard from a box speaker was a pair of floor-standing Nesteroviches. I couldn't believe that such a klunky, traditional-looking speaker could disappear so completely. They were very well set up in a room, oh, 25' deep x 15' wide, with lowish ceilings, not much room treatment to speak of. Horowitz and Ben Webster fully occupied the space behind the speakers. Very impressive. Also they are beautifully balanced, tonally speaking. Nesterovich himself is long gone, unfortunately, but you can occasionally find them used.
I demoed the BAACH system. The tech guy dials in to your Mac and sets it up. They're very nice and offer a ton of support, but I heard almost NOTHING--seriously, almost no effect at all. We talked about my ProAcs and the room, both of which are not terribly bad, IMO. Finally he asked about my hearing, if one ear is different from the other. Most certainly. My left ear is very frequency-limited, and the tech said that will negate the desired effect! I kept the demo for a few days to play for an audiophile friend who has superb hearing, and he could hear the effect very well. But neither he nor I liked the "processed" sound. Bear in mind that this was a rough test in a modest system. It costs nothing (except a temporary charge on your credit card) to try it. Clealry not for me, though.