More power for moderate listening levels?

I have Super HL5 Plus and am currently running them with a 50 WPC tube integrated (ARC VSI55).  They are in my office, so I don't typically crank them up, but with the volume halfway up they are very dynamic and sound great.  At the low level I usually listen, they sound wonderful.  They're not going to fill a large room with sound though with 50 watts and I can't imagine they'd be satisfying with a 25 WPC amp if you want to listen loud from time to time. 

I have used them in my main system with 180 WPC tubed monoblocks and they can go to ear damaging levels, however I think they lose a little finesse. 

One of my friends had 40.2s with a Line Magnetic LM-805iA 48 WPC tube integrated and it was one of the best systems I've heard.  I didn't hear them cranked, but the detail, dynamics, micro dynamics, imaging, soundstage... it was all there. 

A little more quantity wouldn't hurt, but I'd focus more on quality than getting the most watts you can.  That is, assuming you decide you're not satisfied with the levels your current amp can drive the speakers to.

I hadn’t thought of TWO amps!

"You can never have too much power"--probably attributed to Bob Carver, inventor of the Phase Linear 500 and 700.  Sure, they blew-up a lot, but when they worked, they were shrill and loud.

Bi-amp with an external x-over or get two identical amps that will run in mono.

OR, buy a big honkin' solid state amp and rock out, I guess.

Speakers have to match amps in efficiency vs output to be ideal.

 Your dealer should have pointed this mismatch out to you given your desire for occasional high-volume listening.  Has he/she been to your room and listened to what he/she sold you?

Get a better dealer.

Cheers!

I have heard, and liked, the HL5+, and to me, even with lower-powered tube amps, it can play quite loudly.  But, my idea of loud might be different from yours.  In building any speaker, compromises must be made, and I doubt that the HL5+ was designed to have extreme volume level as a strength.  The distortion you thought had been creeping in as the volume got louder might be something in the speaker and not necessarily a problem with the  amplifier you were using.  It would be instructive if you can find a more powerful amp to compare with the one you are using now.

I would personally be more inclined to be looking at amps that sound better at the volume levels I normally listen at, even if it means sacrificing some performance when playing at extremely high volume.  This is how I ended up with three tube amps, the one with the highest power rating being 6.5 watts/channel.