i mean here bro that since listening fatigue after all, may not only be caused by a high level of THD but other factors like cables, speakers, source materials, and even the way you operate the sound system i supposed, and knowing the nature of THD (at least from what we gather from the discussions here...) now, is it really something that we have to be concerned the most to attain good listening? thnx 
I don’t belong to the old school. I am familiar with what avphile1 is discussing. I did in the past what avphile is doing presently – to mention all those technos and try to find the best amplifier that my imagination created. I salivated on those - what his term – exquisite? – amps. But not anymore.
See his part of post:
“…This is actually one of the reasons why getting a very powerful amp, usually above 250wpc, with even relatively substantial distortion products in the 0.1% range, are sometimes prefered, budget and main home line permitting, since you would never really reach that level at your comfortable listening levels…”
You will do this if you do not know what you are reading. A power amp rated 250wpc with no headroom will be surpassed by amp rated 150wpc with 3dB headroom – musically and theoretically. And to think that that 250watter will just sound only twice as loud as my 25watter. But theoretical things will just remain in the mind. So I put his summary in this statement – you can not buy amps knowing all those techno things he is trying to teach the newbies/non-techno audiophile in this thread.
To answer you Jerix, be reminded of the following basic concepts:
(1) You need 10 times power to double loudness (volume) of a sound. This means if you want to double the loudness you are hearing from your 10watt stereo – you will have to upgrade to 100watt stereo – or perhaps upgrade your speaker with +3dB more sensitivity. See, the 250watter is not even twice as loud as a 30watter or more.
(2) What is your speaker – does it has soft dome / metal dome / or no dome at all – is it boomy / no bass / hard to drive – hi sensitivity.
(3) Are you using expensive speaker cable that are normally high in capacitance – or ordinary audio-grade speaker cable.
(4) Some of my research indicated that amps basically will sound the same because their goal is typically the same – to reproduce the audio frequency as faithfully as possible (theoretically). However, this is contrary to reality (practical terms), thus, some audiophile tended to prefer an amp over the other – thinking that is a better amp. But the real crux of the matter is that amplifiers react to different speakers (plus speaker cable - this being inductive, resistive and capacitive variables). Actual testing reveal real performance.
So in my case, I have an 8.3 at fairly 86dB sensitivity rated at 100W – textile (soft dome). I use ordinary audio-grade cable. Thus at 10Watt level, I have my 8.3 at half level loudness already. Would I want to drive it more than that? Perhaps. I will not attempt to load it close to 100W as it is the rated capacity of the speaker. Typically, a 25-watter up to about 75watts is enough for this type of speaker. How much less will it be if it is a 95-dB speaker that you have.
Also, it is the speaker that should dictate what amp to use, not the other way around. Meaning, choose your speaker first – siyempre yung gusto mo na. And when you bought one, find the amp suitable for your speaker. You have the above that gave you guidelines. This time, the amp.
Check amplifier rating – how many watt at what impedance and at what distortion. If an amplifier has published THD of less than 1% in 25Watt minimum – then this is a candidate for audition (power wise). So take for example my RX-V630 – 75wpc at .06% THD into 8 ohms. So the Pioneer, 100Wpc at 1%THD into 8ohms – what I do here is get the half (so it is 50watt), and this is safe assumption this gear is less than 1%THD in 50W – so is also a candidate. Some gears do publish specs like my Kenwood – 68Wpc at .1% THD (yata) and 80wpc at 10%THD into 6ohms. From this, you may note that the power with less 1%THD is higher than the half power point of 40watt (in fact 68watts). So Pioneer would arrive in about 85wpc with less than 1%THD.
You may have heard some people say when they audition the amp – it is forward, laid back, makalansing, mabass – pero they did not describe the condition of their ears. This is short of saying – you must audition your amp with your speaker – torture test it with varied frequency (using your favorite familiar CD using different tracts and different genre of music that you are listening to) and make sure your ears are wide open to note that what you are hearing is in fact what you wanted to hear in an amp.
The THD thingie should have its consideration at an acceptable typical listening power only – 25w to about 75w. If you develop deafness or angry at your neighbor – go ahead, indulge in 100Watts or more. Of course, 100watts or more has some reason – if your speaker is low sensitivity or hard to drive – but then again, high power may not always be the trick for hard-to-drive speakers – the right choice of an amplifier is, THD will not help you here – and this is gained by experience – not much reading the specs. Nowadays, the hard-to-drive speakers are the one sounding very good – but some have rather low sensitivity. THD does not matter at all if you are already enjoying the sound from the synergy of your system.
Do you believe rockers are serious audiophiles? They are usually the ones demanding for high power! You don’t need distortion issue on their amp IMHO. I think their music is basically it.
I hope this helps you doing amplifier hunting the practical way – theoretical specs reading is also good – at least for my comfort room activity.
My advise – don’t shoot your feet.
