Relationship of amplifier sound to transformer quality?

I suppose voltage differences must be very slight. Will the power diodes prevent circulating current in the event the voltages don't match well? I suppose I will check to see how close they are before I proceed.

Voltage differences is highly expected, that is the reason insert power diode in series to isolate both PSU.
It's perfectly normal one PSU supply current to the load all the time and the other PSU kick-in when higher current is required. That is how this configuration works.

That's perfect. Thank you.

That's perfect. Thank you.

As above.
Paralleling power supplies is a problem waiting to happen.