Pass labs xa25 amp and BW 804 d3?

I consider that kind of damping factor pretty ludicrous too. 500 is pretty typical for Pass's mainstream amps, and the XA25 certainly accomplishes that in no small part to lacking any kind of degeneration on the output transistors. 

If the XA25 isn't going to make the power you need, the XA 30.8 isn't either. But that's not why you should choose between them. They're totally different amps. The XA25 is a conventional push-pull topology with negative current feedback. The XA 30.8 is a balanced topology using Super Symmetry feedback. They work and sound totally different. 

I just crunched the numbers for those speakers. 25 watts will yield 101.2dB at 8 feet. That is insanely loud. Nobody listens at that kind of average volume. And 25 watts is just half of it's class A envelope. I crunched the numbers on the amp, too. It seems to be running 24V rails and hits 1% distortion into 8 ohm at about 22.8V. It's current limited to 10 amp, but you'll never see that with those speakers. At their 3 ohm low point that amp will drive 173 watts into them with current to spare. That's like 104dB at 8 feet. If you typically listen at an average volume of 92dB, which is still pretty loud, you only need THREE watts with those speakers at 8 feet. 

Kosst_amojan,
I agree with your calculations and reasoning. This is the point I was attempting to illustrate in my prior post. You can’t look at the XA 25 and conclude, "oh, it’s just a 25 watt amplifier " . There’s considerably more going on here if one can appreciate the design/circuit and implementation. As you calculated, at very reasonable (even generous) volume levels these speakers aren’t demanding much power/ watts at all. And as a reminder, 200 watts/10 amps  (current max) into a 2 ohm load.

DF of 500 is still pretty high relatively speaking in regard to the XA 25. I agree the XA 25 and XA 30.8 are notably different circuit designs. I’ll empathize again, Parasound A 21 or one of the Pass Labs amplifiers, you have to hear them with the specific speaker of interest. Each amplifier will have its own sonic signature with a given speaker.
One point to consider regarding DF is it is inversely proportional to the output impedance (isn’t necessarily a bad thing) and the higher the DF the more NFB utilized (Which ’could’’ introduce some undesired sonic consequences of its own). Another point,  speaker sensitivity measurements are of a single speaker.  Generally 3 db is added when discussing a "pair" of speakers. 
Charles

Seems like Pass has some very knowledgeable owners. 
If they say it can work, who am I to disagree?
B 

Hi B,
If I  am among those you're referring to, I do not own  a Pass Labs amplifier. I'm  just  aware of their design objectives and the very conservative power rating method they employ. 
Charles 

Nelson Pass makes himself extremely accessible. That's why I decided to build one of his amps. Between all the articles he's written, his Burning Amp lectures, and the wealth of information out at DIYaudio in the Pass section, there's a lot of information. He's put enough information out there to clone a Super Symmetry circuit, and some have. He generally doesn't care about that kind of stuff so long as somebody isn't building it for profit. I've never heard the XA25, but it's architecture is similar to my F5, and I've read comparisons between the two to know that the XA25 is a better, more refined version of an F5. Then again, my F5 is more powerful