The only thing I can add is that I wince whenever I read someone say they want to put a tube something (often a pre-amp, but sometimes a buffer) in their system "to add some warmth" or "to warm it up". What an un-HiFi concept! I saw that comment made by Steve Hoffman, of all people. I wouldn't have thought it needed to be said, but apparently being mistaken I'll say it here: "Adding" anything is the very antithesis of High Fidelity, where being as transparent and sonically invisible is the goal.
If you find a system to sound "cold", the solution is not to add warmth, but to get rid of whatever is causing the coldness. First principle's! Real good tube products don't sound "warm", they don't sound anyway at all if they are transparent. The same with real good solid state products, which don't sound "cold". If a component adds warmth or coldness to a system, it is not a perfect High Fidelity product, by definition. While there may be no perfectly transparent components, adding two wrongs to make a right is not a recipe for success. Better to work at minimizing imperfection than trying to perfectly counteract a greater than necessary amount of it in the opposite, also imperfect, direction.
If you find a system to sound "cold", the solution is not to add warmth, but to get rid of whatever is causing the coldness. First principle's! Real good tube products don't sound "warm", they don't sound anyway at all if they are transparent. The same with real good solid state products, which don't sound "cold". If a component adds warmth or coldness to a system, it is not a perfect High Fidelity product, by definition. While there may be no perfectly transparent components, adding two wrongs to make a right is not a recipe for success. Better to work at minimizing imperfection than trying to perfectly counteract a greater than necessary amount of it in the opposite, also imperfect, direction.