MZ wrote: "We're telling you that two amps that *AREN'T CLIPPING* will sound
the same."

Mark,

Some questions.

I assume that different amps will produce varied amounts of audible
distortion when clipping? Enough to hear the differences between them?

This is generally the case. In fact, what I said wasn't entirely true
either. The other situation where a distinction between amplifiers often
exists is at extremely low volumes, where S/N can sometimes be an issue
and where THD is sometimes high. I'm talking about less than 1 watt here.
But I usually ignore these conditions for two reasons. First, at these
volume levels, road noise tends to act as a mask anyway. Second, audible
thresholds tend to change at these levels.

And
why would we care since the aim is to not drive them into clipping to begin
with? Isn't it a moot point?Because I usually don't drive my amps into
clipping. My PG amps deliver gobs of power...especially so since my spakers
are tri-amped. I can make myself go deaf and have inordinate amounts of
CLEAN volume, all of which I'm assuming are unclipped signals due to the
absence of distortion (at least none that I can detect with my ears).

There's probably loads of distortion, but it's coming from the speakers.
This is just unavoidable, really. And sometimes people LIKE distortion.
They choose speakers that produce distortion that sounds pleasing to them
(I'm not talking about speakers bottoming out). There's one paper from
the j.AES that I've got a reprint of that actually examines a listener's
preference between distortion-free music and music with a little
distortion added, and many times the listener chooses the distorted one.
Maybe I'll post a link to the pdf.

Anyway, this issue is important because many folks claim that some amps
sound different from others even when they're not clipping. They claim,
for instance, that a/d/s/ amps are "warmer" and more suitable to drive
midrange speakers whereas MTX amps are better for subs, and so forth.

So what exactly ARE the differences that different amps display when
clipping? If we agree that they behave very similarly at unclipped levels,
then what separates the good from the bad in terms of performance when
clipped?

The spectral content of the distortion can differ between amplifiers. The
key word here is "can". When driven severely into clipping, they don't
always exhibit the perfect signal and perfect flat top that we usually
think of when we think of clipping amplifiers. Guitar amps, for example,
are notorious for generating vastly different sounds when driven into
clipping (which is most of the time). Probably an unfair example because
they have high distortion content to begin with, but it's worth noting
that the differences between them tend to become greater as you drive them
further into clipping.

My summation in all of this is as follows...correct me if I am wrong. As
long as my amplifer gives me enough power (volume) without clipping AND has
the features I want, then it really doesn't matter AT ALL which brand I buy
or how much I spend. (durability aside)

Right.

Also...if I'm not mistaken, Richard Clark has never lost $10K to anyone
during one of his challenges. This alone, regardless of someone's grasp (or
lack thereof) of sound reproduction should clear things up a little.

To my knowledge, he hasn't lost $10k. I haven't followed it too closely
though. It's more of a fun exercise than a properly conducted study, so I
wouldn't draw a whole lot of conclusions from it.