Just to add my experience with the pmc twenty-26,not the same as the twenty-5 but similar. I've had my pair now for around 20 months. I first ran them with 272-xpsdr and now with 300dr.
I only notice a slight sibliance on one or two recordings when I was using a Witchhat interconnect but never spashy treble. Once I upgraded to a better interconnect ( ARsound Lunar eq) I lost any trace of sibliance. I also,found in my setup Tellurium black speaker cables worked better than nacA5.
I have my speakers firing from the long wall in my listening room the room is approx 4mx8m. I have found they need a fair it of room around the back to sound their best, mine are about 0.8m out from the rear wall. Ideally they sound better firing down the long wall as others have surgested but in my room that's not possible. I also found they sound better when toed in to the point the meeting point of sound in approx 1m behind the listening position.
All this is room dependant of course and experimentation is essential. To me the 20-26 excell at imaging, heir mid range is superb, bass is punchy deep and tight but an easily over power a small room. Treble is smooth and detailed and we'll integrated but never harsh or splashy unless the source material is poor, or their are sub optimal components in the chain. When everything is well set up these speakers give a very capable and immersive and we'll controlled performance, in fact they dissappear and just alow the music to flow, what they won't do is make a poor recording sound amazing, they give an honest account of whats presented to them.