Is there any truth to this question?

IMO, the only indisputable comments so far are Pubul57's:

****I have concluded that lower power versions of the same circuit sound better than those iterations with higher power if the power is sufficient to play at a volume you are satisfied with in the room you are using.****

and Tom6897's:

****Absolutes do not exist in audio only in Vodka:-)****

Digepix, to address your question specifically: If the YBA's 50 watts is
sufficient to drive your speakers EFFORTLESSLY, then wether the Krell sounds better or not with those speakers doesn't necessarily have anything to do with it's higher power rating. It may simply sound better because it's a better circuit, or a better circuit for your speakers. Or, it may sound worse; but not necessarily because of it's higher power. Yes, it's true that there is no point in buying more power than needed, but the problem is that what is "needed" is often underestimated.

Curses, Foiled again. I thought for sure there would be just one answer. Is there anything on which all members agree?

"but the problem is that what is needed is often underestimated" and often over estimated also.People usally need 'better' quality and not always more watts.

Amen:)

This question frequently relates to what is often known as the 'first watt'. Many amplifiers have a minimum amount of distortion that occurs at more than zero watts- depending on the amp, it might be a couple of watts and then below that distortion increases.

The most common offenders are push pull transformer coupled tube amps that combine single-ended and push pull circuits, and most transistor amps.

There are certain exceptions- Nelson Pass has his First Watt lineup wherein the distortion continues to zero as power is decreased. SETs and certain OTLs share this property. As an example this is how SETs have attained their reputation for great 'inner detail'.

However the larger you make an SET the less musical it becomes due to loss of bandwidth. This is why the 45-based amps have ruled the roost in the SET world in the last few years. Of course, you need a speaker efficient enough to show that off.

So that leaves OTLs and unique transistor designs that can be scaled up without increasing distortion at low power. IME this is borne out in practice, and certainly flies in the face of traditional wisdom (that smaller amps sound better).

Of course, if you are only listening at higher power levels this may not be a concern...YMMV