There are other, more flexible, and better ways to color the sound, if that's what you want to do. What you are essentially doing here is trying to choose an "equalizer" in the form of a tube amp that you will be paying a lot of money for and want to live with for a long time. Times change, tastes change, different music benefits from different...um...color...so why would to lock into a particular tube amp? Or will you get lots of tube amps and pick the one you like for a particular situation?
The whole thing seems a bit like closing your eyes and shooting an arrow at a target that is moving. You could, for example, get a really good SS amp, then insert resistors between it and your phones. Resistors cost a few cents, even the really good ones, so you could get a couple hundred different ones to play with and end up with your own boutique sound using only passive components. Pick out a few favorites, mount them on gold connectors, insert as desired. Label them "dark", "open", "airy", "vaporous", "glassy", "solid", etc. Now, doesn't that sound like fun? And you be the only one with just exactly those combinations.
Passive...it's such a nice sounding word, isn't it?