Most impact:
1. speaker placement
2. room
If you can't change either of these, then I'd put my money on cabinet design. Most loudspeakers I read about that are known for not sounding boxy have creative enclosure designs and/or driver placement.
This isn't to say these speakers create a better image, but they create sound that's free of the boxes.
Shahinian, Oskar Heil, Green Mountain Audio, Tetra are four brands that come to mind.
1. speaker placement
2. room
If you can't change either of these, then I'd put my money on cabinet design. Most loudspeakers I read about that are known for not sounding boxy have creative enclosure designs and/or driver placement.
This isn't to say these speakers create a better image, but they create sound that's free of the boxes.
Shahinian, Oskar Heil, Green Mountain Audio, Tetra are four brands that come to mind.