More power for moderate listening levels?

The answer to this is complicated.

Can you give us more specifics about your speaker, your amp and listening room?

Do the 2' test.  Sit 2 ' from your speaker and ask if it still sounds strained, if not, it's the room.

Thanks for the quick response.
Pass Labs Int-25 driving Harbeth Shl5+.
Speakers are about 7' apart and about 3'out from the short wall of a 14' x 24' room. 9' ceilings.
My listening chair is 8-9 ft away and this is where I listen most. In this position, instruments are clearly defined in the soundstage and I'm really happy with tone, clarity, and quite frankly the oomph of this little amp.  Occasionally, we will have "dance parties" with the kids and we turn it up and this is when I notice a difference in clarity. At this point, we are much further away and the room could very well be in play. I do not however, listen at these levels in my chair. 
I've been told by a few folks at Pass that the Int-250 would definitely "drive" my Harbeths better. I'm not sure what this means and I remain skeptical. Hence the question: If I sat in my chair where the acoustics are great and I swapped amplifiers while listening at medium levels, would the bigger Pass make a difference? Let's forget about other differences like the 250 being a balanced design. WDYT?

It doesn't work that way, and we don't need to know anything about your room. Geez Louise! This is because amps and power don't work anything like the way the vast majority thinks they do. Its perfectly possible you could find a lower power amp that sounds hugely better at both low and high volume. Class A has nothing to do with it either. These kinds of generalities sound all logical and certain but they break down real fast the minute you hook up the exception to the rule.  

You don't mention the power of your Class A amp. But that doesn't matter either. Unless its like single digits. Because once you get up around 20-50 watts then its not the amp. Its the speakers. If yours are low sensitivity (92dB/1w/1m) then it very quickly becomes almost impossible to find an amp powerful enough to play them loud. Particularly if they are below 90, then you can pretty well forget about it. This is why you see all these guys searching around for the right amp. Its not the amp. Its the speakers.

LOL!!! I was writing while you were writing. First thing I checked, your speakers are hopelessly inefficient. Harbeth has the hutzpah to say they are easy to drive! Not at 86dB they're not! Doesn't matter the impedance! Now you know why you see all these guys in love with their speakers searching searching searching for the amp. Its not the amp. Its the speakers. 

Also notice I didn't need any details. I worked this all out simply based on your first post.

Thanks for the responses. 
The assumption is that the lower powered amplifier drives the speakers just fine at moderate listening levels. My listening says yes.
At the SAME volume, will a higher powered amp improve the sound quality?