Relationship of amplifier sound to transformer quality?

The transformers are not running daisy-chained. They are in parallel which means combined together working simultaneously. If I were to hook them up in series, it would double voltage instead. So yes, It will double the va rating or current capability with a slight loss due to leakage and bring C from 13,600uf per channel to 40,000uf per channel since I will put in bigger caps than oem. An interesting experiment for this kit. This is similar to paralleling an amp for increased current capability vs bridging for increased voltage or output as in watts.

I meant to say similar to paralleling two channels of a stereo amp or in this case a pair of mono amps. However just the PSUs paralled accomplishes the same thing.

They are in parallel which means combined together working simultaneously.

Actually, both PSU will not output exactly same voltages (e.g. one PSU output 55.1V and the other PSU output 54.9V), the one which output higher voltage will do all the work until the current demand from the load is high enough to make the voltage sag to the same voltage as the lower output voltage PSU, then the lower output voltage PSU will start supplying the current to meet the requirements.

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.