Shocked. Need Opinions. How muck power do I need?

It depends. All amps and watts are not created equal, all speakers and speaker impedances are different, and our volume preferences are different. You only need enough power to drive your speakers to the volume levels you prefer in your room. Headroom is nice if you push dynamic passages to higher volumes, but most of the time I don’t come close to the limits of my amps.

Even with speakers of average sensitivity (~ 89db), over the years I’ve gone from a high of 255 watts per channel (Hafler DH500) down to about 17 watts per channel (tube triode), and my current amps sound much nicer to me than any other more powerful amps I’ve owned. In fairness, for bass heavy passages an ample size SS amp tends to handle big bass peaks on large woofers better than my small tube amps do, but that’s one aspect of the overall sound spectrum (below 80hz in my case)

one of the rare threads in which everyone seems to be making good points. my own experience, which matches other posters', is that high current delivery is by far the most critical factor--even with demanding speakers like dynaudio i've heard 50w pass amps outperform amps with much more wattage.

@loomisjohnson  - I can believe that, but also Pass I think likes big old school speakers.  See if you can find Pass' article on damping factor and whether it really should be low or not.

I once tried my little Onkyo from my bedroom system on my Maggies. It's rated at 44/70. To my amazement, it was really good! That little Onkyo is a gem.

In some ways, a high performance amplifier is like a high performance race car. It needs to accelerate instantly and then stop on a dime - without swerving off the track.

Transient response* is an important factor in amplifier design.

In audio, an example would reproducing a 96 piece orchestra that’s reaches a crescendo, then pianissimo. The finale of Gershwin’s ’Rhapsody in Blue’ would be a good example.

Other examples would include: hearing a close-mic’d plucking of a guitar string - or - the thwap of a drum stick hitting a snare drum - and then the decay that follows. Does it sound like the real thing? A good synergy between the amp and speakers will define that. Much depends on the kind of music being listened to and the priorities of the listener.

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* In electrical engineering and mechanical systems, the transient response refers to the temporary behavior exhibited by a system when subjected to a sudden change or disturbance in its input. It encompasses the system’s reaction to a stimulus before it settles into a stable, long-term state¹. Specifically:

• Rise time: The time required for a signal to change from a specified low value to a specified high value (typically 10% to 90% of the step height).
• Overshoot: When a signal exceeds its target value.
• Settling time: The time for the output to remain within a specified error band after an ideal instantaneous step input.
• Delay time: The time required for the response to initially reach halfway to the final value.
• Peak time: The time to reach the first peak of the overshoot.
• Steady-state error: The difference between the desired final output and the actual output when the system reaches a steady state¹².