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

Power supply. Power supply. Power supply. 
 

Bigger amps, have bigger power supplies. Depending on how loud you are listening, as has been said above, it’s about current driving the difficult parts of the speakers load. 
 

Smaller amp could work, if it has a power supply capable of delivering the goods…

Always have much more power then you need ,good rule of thumb 

for if playing loud you don’t want to be going into transformer saturation and distortion , they say in transients you can have 10 x the power for short burst 

in transients milliseconds ,the power supplies and. Ample capacitances is very important .150 8 ohms 300 at 4 ohms is a solid amplifier double down 

if it cannot come close then average at best performance .the output-devises  such as how many Mosfets per channel will dictate current delivery to complement the transformer size ,and filter capacitance. My Coda amp 3k transformer ,almost 100 k in filter capacitances ,and 20 15 amp Mosfets  per channel , 100 amp  capability .

it has dual 16 amp slow blow fuses on the back that says a lot about current delivery and 4 more fuses inside the unit.

if tube then calibrated different for the size ,quality of the power transformers  and chokes ,power supplies. from my experiences which is over 4 decades .

With 40W it will be -2.7dB.  Perceived loudness will be 16.6% lower (still over 100dB)

I listen to Mostly Jazz and some rock and I bet I don’t go past 5 watts 90% of the time. I actually have two systems.  one has 40 watt mono blocks and it can blast you out of the room the other has 300 watt mono blocks and I bet I’ve never used 100 watts. I also have a subwoofer, that I rarely use because on the upstairs system, I rarely need it.  So it’s probably going back into the downstairs system.

I believe my Pass X250.8 pushes about 12% class A and I never had any needs to out of it. About 30W is plenty as long it is backed up with huge power supply and enormous banks of capacitors