so what actually happens here with two parallel wires from the power supplies, is on the positive wire, electrons flow from the load (the speaker) through the output transistors, into the power supply during the positive half of the cycle, during the negative half, electrons flow the opposite direction, but in the negative wire. the net magnetic field around the pair of wires is the same frequency as the current through the load. if you are thinking the other power supply wire picks up a signal through magnetic interaction, this is possible, but is "eaten" by the large power supply capacitors if it has any effect at all. the coupling between the supply rails is quite small, and essentially the filter caps absorb it in any case.
if you are trying to reduce the effects of crosstalk between the power supply rails and the input stage of the amplifier, this is a layout problem, not a circuit topology problem. keep the circuits from input stage to voltage amplifier stage (the voltage amplifier is a high impedance node) out of close proximity to the high current portions of the supply rails, keep the power supply wires to the output stage as short as possible. adding some ground plane around sensitive portions of the amp circuits (if you happen to be designing a board), and possibly routing the supply wires through a steel partition between the amp and power supply can be useful in minimizing magnetic coupling of power supply currents to the input stage and VAS.
if you want more specifics, find Douglas Self's Audio Power Amplifier Design Handbook. he has at least a whole chapter on proper layout of power supply and power wiring. i recommend you get the latest edition of it, but if you are on a tight budget, you can find an older copy of it here:
https://archive.org/download/fe_Aud...sistor_Amplifiers_Design_Handbook_D._Self.pdf
it's the third edition, and the latest edition is the sixth edition, with a lot of newer information (50% larger than the 5th edition).
the third edition still has a lot of good information, especially about what your question seems to be. i once worked for a company that made excellent amplifiers, and as part of the final test procedure, we used a BIC pen body with notches cut in it to move the power supply wires around, then hot glued them in place. the procedure was done with a distortion analyzer, and the goal was to null out the magnetic coupling between the power supply wires and the input stage. the procedure worked, but i'm willing to guess that changing the routing of the wires might have made that time consuming procedure unnecessary. the procedure was done at 20khz (the magnetic effect is more pronounced at 20khz than any lower frequency, and has a 6db/octave slope)