Pass labs xa25 amp and BW 804 d3?

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 

Thanks for your very informative posts, Kosst. I’ve learned some things from them about my own XA25 that I didn’t know previously.

Regarding the references in one of your posts to "average volume," others should keep in mind that what matters with respect to an amp’s maximum power capability is of course the maximum volume levels that are reached on the recordings that are listened to, not the average level. And the relation between the maximum and average volume levels will vary dramatically among different recordings, depending on both the music and on how much dynamic compression has been applied in their engineering.

For example, some classical orchestral recordings that have been engineered with minimal or no dynamic compression may reach brief dynamic peaks that are 30 db or more greater than the average level of the recording. Which in turn means that around 1,000 times as much power will be required to reproduce those brief peaks compared with the amount of power required to reproduce the average level of the recording. While many and perhaps the majority of pop and rock recordings are compressed to a dynamic range of less than 10 db, which will require less than 10 times as much power for peaks than for the average level.

Thanks again. Best regards,
-- Al