The external PSU is a great idea.
Move the switch, the fuses and the rectifiers to that separate box as well. You could also have some capacitors for additional filtering in that box. This would make something like a CCLC filter. That additional capacitance would also compensate for the 1.5mh instead of the 2mH, but don't be too worried about it. To connect the two boxes you could use XLRs (rated 50V and 16A).
The wires from/to to the rectifiers carry AC. Of course the wires from the rectifiers to the boards have less ripple-voltage left (before the choke that is), but still, they are running close to the inputs' wires which may pick up noise this way.
And if you want to add some extra caps in the external PSU the rectifier-bridges would have to be there anyway.
With 55000µF caps and extra inductor of 2mH(total 3,5mH) almost death silent,you have to put your ear against the loudspeaker.
With 70000µF and extra inductor of 2mH(total 3,5mH) death silent
