How big of a difference do amps make?

Steveaudio hits the nail on the head. What are you doing with a 'cheap' cdp and thinking about a better (or different) amp. I have little doubt that the Thor will sound better, but why bother if you really can make a much bigger change with a new CDP.

But that said, if getting the Thor (or any other amp which you feel is better for your Merlins) is just your first step in getting ready to seriously explore quality (not necessarily expensive though) CDP's have at it.

I can't recall how often I've said this. Once you get used to the attributes of all your other gear, guess what you then start listening to, again? Your amp. Which will always be the most identifiable piece of gear in your system. You will hear through every other piece very quickly.

Csontos, that may be so but I think it is too bad if it is so. In a given system if I start looking for sonic changes with the speakers I always look at sources and ancillaries first. But having anticipated what you suggest I only use tube amps where I can, for a few bucks, make minor changes by just using different tubes. A cheaper way to skin the cat I think. :-)

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.