Is powerfull Amps only for low sensitivity speakes?

Kosst_amojan,
I completely agree with your comments. Those who recommend "the more power the better" promote and provide misinformation . So much depends on the design and characteristics of the specific speaker. Some speakers will clearly sound much better with tube amplifiers driving them and/or lower powered simple circuit class A  solid state (for example, First Watt or Valvet, etc.).

On the other hand some  speakers will definitely require amplifiers capable of higher power or higher current delivery. The load characteristics of the speaker is the vital determinative factor. To suggest that any high power solid state amplifier that measures well will be all that’s needed for "any" speaker is poor advice and in my opinion a disservice to those seeking meaningful advice. Kosst_amojan I hope people take note of your well reasoned reply.
Charles

+1 Kosst.

I can only give you my experience which is a reflection of what I believe Koost is saying. In short its about synergy. IME, my low powered systems have sounded better. IE, I had a Conrad Johnson MF2500A (250wpc) paired with a CJ PFR preamp.It sounded good with my Silverline Sonatas 93.5db. But I got an urge to try tubes. So I bought a fully modded Dynaco ST-70 just to dip my foot in to see what all the fuss was about for tubes. Its a mere 35wpc. Guess which amp kept?
Another amp which shined brightly in my system in the late ’70’s was a Harmon Kardon 45wpc Solid state. It was paired with large Advents and later Infinity RS series, both 89db (I believe) 

2. Is there any *disadvantage* to powerful amps with efficient or small speakers? No.

There is nothing about a powerful amp that is inherently a compromise of sound for power

These statements are not accurate. If the amp makes too much power and the speaker has no need for it, the amp will be operating in a lower power region. With most higher power amps, this means it will have increased distortion. You can see this in their specs. The increased distortion is audible as brightness in most cases and will result in less detail as the distortion will mask lower level signals.

@obatu Your speakers are only 92db; that is a moderate sensitivity- high sensitivity would be more like 98 or 99 db at a minimum. An amplifier of the power you mention will be no worries.

Just look at the Audio Precison graphs at different power output levels of a 2x350 watt Yamaha p3500s pro audio amplifier: http://www.homecinema-fr.com/forum/amplificateurs-de-puissance-haute-fidelite/mesures-ampli-yamaha-p...
It is true that distortion goes up a little bit at lower levels, but it is still very low and below the noise level: 0.05% at 100 mW. Look at graph 16 in particular, for the output range of 480mW to 7.7 W rms. In that range it never gets above 0.015% and rapidly descends to 0.01%. There is no way you can hear this.