Is powerfull Amps only for low sensitivity speakes?

Some speakers require amplifiers with a higher damping factor (DF) and some speakers sound their best with lower DF amplifiers. The desirable level of DF is determined by the speaker design and the intentions of the speaker builder.

You can increase DF and inversely lower amplifier output impedance by utilizing more NFB. Some amplifiers tout DF level of 1000 or even higher. This ultra level of DF doen’t correlate with better sound quality.

There are speakers that sound superb driven by amplifiers with a DF of 2 or 3. It all depends on the speaker design mandate.
Charles

I reject the notion that inefficient speakers are inherently superior sounding. Not based on my listening experiences. In terms of sound quality there is much overlap between various categories of speakers . Low, moderate or high efficiency,  excellent sounding speakers exist. 

Now someone may prefer lower efficiency speakers and of course that’s fine. I just find that people who post very generalized blanket statements do reveal a lack of knowledge for a given topic. Ironically their blanket statements are presented as indisputable fact which they most clearly are not.
Charles

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