How big of a difference do amps make?

OK:

http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php

The Merlin is designed on and for tube amps and is friendly to all tube amps as long as they make enough power.

The folks who love tube amps just like the colorations..

This is incorrect. The folks that love tube amps have discovered that they enjoy a larger soundstage, greater detail and don't like the coloration known as brightness.

Tubes can be guilty of richness (coloration) due to 2nd ordered harmonics, but it is a matter of design (not the fact that it is a tube amp) that controls whether or not this will manifest (for example our amps lack this harmonic entirely due to their fully differential design). OTHO transistors exhibit odd-ordered harmonics that tubes don't; due to the way our ears perceive sound this comes off as brightness even if the odd ordered harmonic content is barely measurable.

Additionally, modern day tubes need not be expensive. Our M-60, which is very popular with Merlins, is about a little over $350 to replace the output tubes in both channels.

What we learned here is that both tubes and transistors exhibit colorations. With tubes they are easier to control.

'Coloration' usually refers to a tonality. 'Richness' in the midrange is a common coloration caused by the presence of a 2nd harmonic in tube amps.

The ear hears harmonic distortion as a tonality.

It is also the most sensitive to bird song frequencies, and uses odd ordered harmonics to determine how loud a sound is.

As a result it is more sensitive to these harmonics than any other phenomena of sound; much more so than human vocal ranges!

So if the equipment makes odd ordered harmonics, even in vanishingly small amounts, we hear it, and have words for it: harsh, bright, hard, clinical, etc.

We hear lower ordered harmonics (2nd, 3rd and 4th) as richness. The ear finds these harmonics less objectionable; in tests people will not complain even if 30% 2nd harmonic is present. That is not entirely true with audiophiles- hence the 'tube coloration' of Elizabeth’s post.

Thus the tubes/transistor debate, ad nauseum.

The other part of the coloration issue relates to the Voltage and Power Paradigms, the link to which I dropped in on my first post in this thread.

If you mix equipment from the two camps, you get a tonal aberration. This is the amplifier/speaker matching conversation that we also see a lot.

Yes- naturally, real instruments have sounds composed of both even and odd-ordered harmonics :)

Mrmb, if you have Soundlabs, you might want to know that Dr. West has made a change to the back panel that has resulted in the speaker being a lot easier to drive! In addition to being easier to drive it also sounds a lot better and is a more beneficent load to the amp.