It's a very good question that I really had to think about. I would say decouple first then couple perhaps if all else fails.
That's not to say that coupling might not sound better in some cases but each case of coupling will produce different results. So how can a speaker be designed to couple when every case is different? Therefore decouple to achieve what was intended best. In most cases coupling will result in hearing the room more rather than just the speakers.
I recently added a pair of isoacoustic speaker stands designed to decouple and these have helped make a believer out of me. I then added a pair of auralex sub dude isolation platforms under my ohm speakers in my family room with common suspended plywood flooring and the results in both cases are a revelation.
That's not to say that coupling might not sound better in some cases but each case of coupling will produce different results. So how can a speaker be designed to couple when every case is different? Therefore decouple to achieve what was intended best. In most cases coupling will result in hearing the room more rather than just the speakers.
I recently added a pair of isoacoustic speaker stands designed to decouple and these have helped make a believer out of me. I then added a pair of auralex sub dude isolation platforms under my ohm speakers in my family room with common suspended plywood flooring and the results in both cases are a revelation.