More power for moderate listening levels?

OP I was in the same dilemma not too long ago. My current set up, which I settled for is a small office (14x8) where I do low to moderate level listening. I have Harbeth p3esr and Croft Integrated amplifier. The pair excel and I mean excel in low to moderate level listening bringing out the best. Non-fatigue hours of listening with the perfect amount of details and warmth. 

As soon as I took the set up to my living room and throw a little party with the family it was a massive disappointment. There are a multitude of factors why that happened. The music genre changed and the power given to the amplifier changed in a much larger room. 

Harbeth p3 struggle with dance, electronic and rap music at loud volumes driven with an underpowered amp. I plugged in my 300w/channel earthquake amp followed by 180w/channel sim Audio W5 amp. Big difference - but that's where the p3 limitations kicked in. 

My recommendation - keep your dance party/family/home theater gear separate from your intimate listening room. I am very happy with my party/home theater room set up with Von Schweikerts VR4 speakers and Sim Audio w5 and Earthquake amp. 

Hope this helps somewhat. 

As opposed to choosing what is bad, I guess. Like tuberculosis.

@millercarbon 
Yeah, you named it. Now you will have it for the foreseeable future.

OP, many posters want you to buy what they have in speakers and amps. Sure that would be great.

It would be worth it if the reserve power of the new amplifier improved sound quality at all levels.

Yes, that is it. But if you are happy with your speakers as you seem to be, add more power. Same brand amp, different brand amp, what ever. Don't change your speakers, get more power. You'll be happy.

I'm hoping the higher power amp (15W Class A before switching) shares some of the sonic character of the current amp.

Class AB amps don't 'switch' per se. The slide into Class B. Depending on the design and the load, the transition can be smooth and less so.

Getting AB bias currents exactly right as the amp plays is an engineering challenge. It almost always lags the amp's thermal state. Manual bias amps are frequently mis-biased from the factory as the amp is set up with the covers off in an environmentally controlled lab. Close it up and stick in a rack and all bets are off.

see https://www.zenmod.in.rs/pass-labs-x150-5-checkingadjusting-offsets-iq-and-gain/ for a Pass 150.5 bias adjustment tutorial.

Like many other recent 'inventions', 15W Class A before switching is nothing more than ≈30mV bias across 10x 2Ω emitter resistors in ± amp halves.

Pass is a brilliant designer with an impeccable pedigree, so his designs are likely SoA.

@ieales, it would not be polite to tell you what I think of Tekton loudspeakers. 
I am pretty sure most speakers are destroyed not by raw power but by clipping. Certainly you could just plain overpower a driver but most people do not have that kind of power. 
I am not an electronics engineer but my JC 1's biased for 25 watts class A get hot enough that you can not keep a hand on the heat sink. That has got to be a lot more than a few mV bias. 
Who in their right mind would put a class A amp in a rack? Even millercarbon would not do that:)