I have, for many years, espoused the notion that a power amplifier is more power supply than power amplifier. Conventional thinking places the amplifier part of an amp as the most important and its power supply as secondary.
In my opinion, that's backassward.
The amplifier part of a power amplifier is most easily thought of as a valve that connects, in varying degrees, the power supply to the loudspeaker. Thus, the quality of that power supply is critical.
Which is one great reason why the only real difference between a stereo power amp and a monoblock is the power supply. Amplification circuits in our stereo versions are identical to their monoblock counterparts.
Monoblocks are better (mostly) because they do not share a power supply.
Put another way, if you had two stereo amplifiers and you only used 1 channel of each for the system, you'd be pretty close to the performance of a monoblock.
It's mostly in the power supply, baby!