Is there any truth to this question?

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

IMO excellent comments have been made in many of the posts above, but with respect to the general question (as opposed to your specific situation) I would particularly emphasize these:

02-13-12: Frogman
If the YBA's 50 watts is sufficient to drive your speakers EFFORTLESSLY, then whether 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.

02-12-12: Grannyring
Extra watts and headroom can be a very good thing especially with large orchestral music and the like. Same is true for solo piano turned up to louder volumes.

An important variable is the kind of music that is listened to, and in particular its dynamic range (the DIFFERENCE in volume between the loudest notes and the softest notes). Wide dynamic range material, such as well recorded, minimally compressed classical symphonic music, can require vastly more power to handle brief dynamic peaks than small scale vocal, chamber, or jazz recordings, or dynamically compressed rock recordings. And even if a lower powered amp has sufficient power to avoid clipping on the peaks of wide dynamic range material, it may show evidence of strain on that kind of material that would not be brought out by material having narrower dynamic range.

On the other hand, if everything else is equal, more watts = more $, so investment of a given number of amplifier $ may result in higher amplifier quality if applied to a lower wattage design. But of course everything else is rarely equal.

In your particular case, I suspect you would do better with the YBA amplifier, based on your music preferences, your listening room size, and the comments about the specific amplifiers by Charles1dad (whose opinions I always have great respect for).

Regards,
-- Al