Sorry Mitch you been had, this is A/B what you think is Class-A.
"Class A Operation / Fully Balanced / XLR Inputs Only"
This is not an indication of 300w Class-A.
"300 Watts continuous rms into 8 ohms"
This is an indication of rms watts Class-A/B
"Power Consumption: Low Bias Mode - 300 Watts"
This is the "power consumption", not the Class-A bias
"Power Consumption: High Bias Mode - 800 Watts"
This again is the "power consumption", not the Class-A bias
If this amp had the Class-A bias you think it has it would be the size of a house!!
Here is an example of what heat sinks are needed to have just a 25w Class-A mono block amps with nothing over 25w (no Class-B at all) if it were say 50w of A/B the "heatsink area" for the same 25w of Class-A would more than double.
They are the famous 25w Class-A Mark Levinson ML2 monoblocks, but that’s all they had 25w!!!!
https://ibb.co/d6zvmMRCheers George