Well, there are external and external changes to consider. Much of above are good suggestions, I'd add ball bearing type footers, they always add air and spaciousness, however, may change timbre to some extent. But then timbre changes are concern with every isolation device, and I've tried every one of common designs, hanging your equipment from ceiling best, but of course that's silly suggestion in this instance.
In the end you could try every external change possible and may find same issues remain, and this is quite possible. Resistors, capacitors, diodes, voltage regulators, internal wiring, IEC receptacles, fuses, binding posts, I may be missing something. I've done everyone of these mods at one time or another, biggest bang for buck in general terms are capacitors, I'll put the rest in similar category, although some may have more effect than others in certain situations.
You're trying to gain more spaciousness, air. I've been in same position at another point in time. I'd start with coupling caps, may want to try something with silver, or combo silver/copper, Mundorf or Duelund here. This will most likely add exactly what you need on top. Resistors may be next move you'd make, depending on what QS is presently using, he may be using carbon comps, nice warm resistors, may be part of dark issue. Everything else would be of secondary importance.
I pretty much guarantee contact with OEM will not go well, they'll be offended you want to change what they consider optimal implementation of their design, you're trying to alter their child. I know this from experience, and this even if they later adopt your modification!
Also, do only one change at a time, do the caps, nothing else, listen for at least 200 hours, only make further changes based on what you're hearing at this point. You may not have to make any further changes.
Always remember that every single one of these changes may alter sound quality in ways you may not like. Change may also help in one area, not in another, so many parameters of sound to think about! For instance, you may get more air, spaciousness with certain capacitor, but it may alter overall timbre in ways you may not like. Changing out parts is like food recipe, a little of this or that may make all the difference, you need to be prepared to alter things as you go along.
All my warnings are just things to be aware of, parts changes can take a certain piece of equipment from temporary to permanent solution.
