What decibel level do you listen at? What is ideal?

@jonwolfpell  agreed, Pass designs like my XA30.8 are totally sufficient at lower wattages even for higher spl listening.  I also have subs which really helps take the strain off the amps.  I've blasted it loud as hell and haven't seen the needle move.  I would say though "powerful" is relative and there are other things than wattage to consider like toroidal capacity and how much amperes it's rated for.  Along with so many other things... although some inefficient speakers DO really need that extra juice @ghdprentice and from the same manufacturer, yes more wattage is typically better for inefficient speakers and also has to do with other things like ohm load and impedence matching with the preamp to the amplifier

@larsman I meant more like a physical one - check out BAFX spl meter on amazon or wherever you care to shop.  It has served me well and is not expensive.  My friends phone can be wildly off vs an actual calibrated meter.  Best of luck to you!  I'm always curious myself at volumes but if you're listening quietly it doesn't matter that much.  Your ears will tell you when it's getting loud

Thank you again, @jrareform - yes, I see they are about $17; I'll order one - I've got loads of Amazon points! 

@jonwolfpell 

Yes. That is exactly what I am saying. 

I have never been a fan of Carver. But I remember decades ago him doing a demo of the sound of (I think this is right) a set of scissors cutting a piece of paper. He was able to measure the near instantaneous power demand to reproduce this sound (as opposed to normal gauges that are long term averages in comparison). Any the really large amp clipped during the snip, restricting the dynamics of the sound reproduction. 

That is the logical side. Then I have heard multiple versions of the same amps with the same speakers... and they sound better... so that is holding all other things constant. This have always been solid state amps. We are talking normal speakers... sensitivity 82 db to 96db. I have never played with 100db sensitive speakers... there could be some down side with speaker that sensitive. 

For the amp power levels question - I don’t even know anymore lol. Sure with "all else being equal", more power is better. But unfortunately in this hobby, there is abosolutely never an "all else being equal" scenario! Some specific scnearios I’ve experienced, which makes it impossible to correlate (or not correlate) sound quality to power:

• I now have some restored Eico HF-22 tube amps, rated a paltry 22 Watts, that sound like heaven into any 91dB+ speakers. Even at my preferred (loud) SPL volumes, they'll spank most higher-powered amps, to my preferences.
• Several years ago I (briefly) had the Carver Sunfire Signature 600 II amp (600 Watts / 1200 @ 4 ohms) and at least to me - it sounded like the sonic equivalent of rubbing broken glass on my face. 
• My favorite amps - at any price - are the high-end, high-powered VACs - Master and Statement lines. These amps also sound significantly better than VAC’s lower-powered, lower-tier amps - but there are many more differences than JUST the power, so it can’t be isolated to just that. But wow - it's quite frustrating going from the Signature amps to Master / Statement line amps, if you ever have to go back to the former. 

It’s quite possible that some amps designs / topologies simply sound better when scaled up a lot in power. But then others...don’t. The Eico is an an example of an amp that sounds "good to the last Watt" (lots of focus on the "First Watt", but this can be important too). Others amp may require gobs of headroom to say out of a trouble zone. And some amps will just sound bad to you with your speakers, no matter what!

I would be very curious to hear an A/B demo of a variety of speakers only playing at lower volumes, say 70 db, with both high quality , high power solid state amps vs high quality, low powered tube amps. I would not be surprised if the for the first few watts ( maybe that many on peaks at that low volume) , the tube amps sound better, fuller, richer & more 3 dimensional.