Counterargument: The power supply is overrated. You want to start with high-power but lousy switching power supply. You want to position it far and shielded fro

Counterargument: The power supply is overrated. You want to start with high-power but lousy switching power supply. You want to position it far and shielded from your amplifier. You want a decent ferrite bead on the cable, and a decent bypass filter in the box (both electrolytic and ceramic). The high-frequency stuff should mostly be gone. You can then use a linear regulator and a pretty basic filter to clean up the rest, and introduce an extra volt-or-so of drop on the output. It sounds like a lot, but it's not.