What is your experience with amp power?

Mono-blocks>bi-amp

That is generally my experience as well, though some solid state amps will sound worse when "bridged" to mono. With tube amps I’ve definitely heard substantial improvements going to mono. If the amp was designed to be a monoblock (not switchable), then you’re golden.

Having that head room and power even with highly efficient speakers make for a much better listening experience. No straining, no clipping, ease of presentation. In my experience my Tannoys are 95 db efficient and I drive them with a 500wpc McIntosh amp. When I first got the amp I thought it would literally blow me out of the room, but that wasn’t my experience. I think I’d be hard pressed to go down in wattage.

Yep, same here! Big Tannoys with a lot of quality power behind them => limitless dynamics, lifelike sound :)

I know my Tannoys can sound great with 25 - 35 Watts, I used to do that, but when you hit a need for power these amps won’t be able to deliver no matter their PSU design. Certainly, one could get through a lot of musical material before hitting a dynamic transient that’s going to either cause compression or hard clip on that lower power amp (yes, tube amps can hard clip too). But it’s there. Vinyl setups also have to content with higher playback power demands from feedback, warps and resonance issues - you try to mitigate this but it’s always there. More power freed me from these issues - and then I also noticed the other benefits of cleaner, lower distortion, and extended frequency range playback from the extra headroom. When you hit a huge dynamic swing, +10dB or more can happen very quickly, and while your 35 Watt amp could melt your ears off all day with with KISS (with no dynamic range) you’d really need 300 Watts to play that orchestral peak cleanly.

I do not like high efficiency speakers, because they usually have poor dynamic floor. It's a trade-off. Heavier speakers can get a lot better dynamic range from quiet listening to very LOUD.

@czarivey 

High efficiency loudspeaker usually have greater dynamic range than less efficient speakers, due to something called 'thermal compression', which is heating of the voice coil. As the coil heats up, its resistance goes up too. This is far more common with lower efficiency loudspeakers! Most solid state amps will thus put out less power. This can happen with individual bass notes, causing them to compress.

Its often more difficult to find higher power amplifiers that actually sound like music, although that problem is not as big now as it was 20 years ago.