Primary concern is Turntable of course.
Let's over state the case that 99% of setups have equipment between the speakers.
Music (mono or stereo): there are no center vibrations generated, only the illusion of center, by weak/strong/equal left and right vibrations, so, center can be best.
Video (mono, stereo or surround), Center Channel Speakers and/or TV Speakers, main L/R speakers definitely located just above and beside equipment.
This is another reason I am not in favor of side, rear or downward firing drivers, radiators, ports, or subs. The lack of direction control especially with corner's random reinforcements is often problematic.
Subs, Music or Video need to be chosen/located with equipment vibration a large consideration, which is why I prefer front firing sub located away from the equipment, in my case on my end of the room, it's front and side blocked from me.
The flexibility of your floors and floor/wall connection should influence whether you couple or decouple your speakers to the floor, and couple/decouple your equipment to surfaces, especially TT.
Speaker enclosure design, to get 'all' vibrations toward you via the drivers, none transmitted by the case itself or movement of the entire case is always best IMO.
