Tubes are as much of a musical instrument as a thick overdriven electrical guitar. Transparency is not the name of the game in my book, musicality is, and I'll take tube distortion and all the fun things that tubes bring to the table.
Speakers, room size shape and treatment, they come first by a mile. But there are differences to be had throughout the entire chain (except cables :p, get a competent cable and call it a day).
Redo, an amplifier isn't a musical instrument. All that it does to make the music "come to life" is to increase the input voltage about 25-30 times so that it's loud enough to hear. All amplifiers do this. One which would make the sound different, rather than amplifying transparently, would either be incompetently designed or damaged. A basic principle of audio technology, well-summarized by the Audio Critic, is that
"Electronic Signal Paths Do Not Have a Personality!".
