Class A biasing is beneficial when it comes to sound quality, but there are many, many other things that it affects, most notably reliability: constant thermal cycling leads to failures. Biasing is a thin veneer spec that has just a fraction to do with the overall sound and character of an amplifier - it's a detail, not a foundation.
My Boulder 1060 operates up to 17 watts in Class A before switching to Class AB, however Boulder spent a lot of time perfecting the circuit design & notching out crossover distortion. The Rowland 625 for example runs in Class A up to a higher power output level, although in reality this means very little - the biasing scheme used to keep an amplifier in a particular mode of operation can't make up for for an overall amplifier design that's not of the same calibre and may actually be necessary to compensate for non-linearities in operation. In other words, if you start out with a much better circuit design to begin with, you don't need to over-compensate with higher biasing.
My Boulder 1060 operates up to 17 watts in Class A before switching to Class AB, however Boulder spent a lot of time perfecting the circuit design & notching out crossover distortion. The Rowland 625 for example runs in Class A up to a higher power output level, although in reality this means very little - the biasing scheme used to keep an amplifier in a particular mode of operation can't make up for for an overall amplifier design that's not of the same calibre and may actually be necessary to compensate for non-linearities in operation. In other words, if you start out with a much better circuit design to begin with, you don't need to over-compensate with higher biasing.