2. Is there any *disadvantage* to powerful amps with efficient or small speakers? No.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.
There is nothing about a powerful amp that is inherently a compromise of sound for power
@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.