Not that it matters in the least, but the cables will be more exposed to static electricity when in the air insulated from the floor. The better the separating insulation the more chance for static electricity.
Why do you think that static electricity has anything to do with audio electronics?
Oops! I should have written 'meaningful change'.
Of course now with high resolution test equipment, over time, temperature, humidity, voltage and current there very well may be measurable changes in any part or unit.
With the exceptions of vacuum tubes, transducers, mechanical moving parts and some electrolytic capacitors, NO the don't measurably change.
With the exceptions noted above, electronic units don't deteriorate.
As 'Folsom' just pointed out. Short AC cords & cables from hi-fi component to component means short Safety Ground conductors with the attendant low end-to-end resistance and small ground loop area.
Only large home theater or huge power amps need more than one 20 Amp circuit.
Have him run a 120V feeder to a central location in or near the audio room. Then a small breaker box for the 3 breakers.
One size larger cables are always good.
If you are going to use a large isolation transformer (wired as a Separately Derived System) then make it a 240V feeder, but only...
Actually ithe AC power current goes from the big power company transformer down the street, thru wires, cables & cords and breakers then to your hi-fi components after which it again goes thru wires, cables & cords and breakers to that big transformer.
As for 'ground' as in Planet Earth. None...
When you write cable design, do you mean?
Unbalanced analog audio RCA interconnect
Balanced analog audio XLR interconnect
Unbalanced digital RCA interconnect
Balanced digital XLR interconnect
Loudspeaker cable
AC power cord
The needs of each are different and the best design standards for each...