Freediver clearly isn’t familiar with those speakers.
I power 936’s with a 32 watt class A amp and I’m only doing that because it’s push-pull with 32V rails. You will melt your tweeters with distortion trying to get solid volume out of those with a 15wpc single ended amp. But since somebody doesn’t want to believe me, I’ll go through the math.
Those are about 89dB/V/M sensitive, but they have a low point of 4.6 ohms. I’m going to round that to 4 for simplicity. That means they want 2 watts to make that 89dB at a meter around the low point. That mean you need 8 watts at 2 meters or 6 feet away. And then you need 32 at about 10 feet. And that’s assuming no transients that exceed the mean volume. 15 watts is ok if you feel like wearing them like big headphones, but you’re using yours in a room roughly the same size as mine and I’ll bet you’re 8 to 10 feet from them. 15 watts isn’t enough. Period.