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.