I've found Joseph Audio to be consistenly good in the disappearing act category. Audio Physic does well in that area too, along with many of the others already mentioned.
Haven't read all the other posts, but inert stands and sweating the details in positioning are obvious starting points. The other thing is that a lot of manufacturers don't go the extra mile to ensure all drivers are matched to very tight tolerances, and I think that could also play a role here.
Lastly and maybe most importantly I'd also mention the room itself. In properly treated rooms images most always seem to be locked in solid, and if a room is not properly treated I find it can be a crapshoot and I too often find myself shifting my head a little left or right to lock things in (especially the center image). As is so often stated here, a treated room is probably one of the most important and most commonly neglected areas in our hobby. I'll also second Newbee's comment about ears not always being perfectly balanced -- good to get that checked especially among us audiophools.
Haven't read all the other posts, but inert stands and sweating the details in positioning are obvious starting points. The other thing is that a lot of manufacturers don't go the extra mile to ensure all drivers are matched to very tight tolerances, and I think that could also play a role here.
Lastly and maybe most importantly I'd also mention the room itself. In properly treated rooms images most always seem to be locked in solid, and if a room is not properly treated I find it can be a crapshoot and I too often find myself shifting my head a little left or right to lock things in (especially the center image). As is so often stated here, a treated room is probably one of the most important and most commonly neglected areas in our hobby. I'll also second Newbee's comment about ears not always being perfectly balanced -- good to get that checked especially among us audiophools.