Tube sound is not about warmth. It's about correct presentation.

But what is it in the sound that gives this?   It is not just more harmonics as that is synthesized in modern DACs and it is no where near the same. It is not linear distortion as tubes can be as flat as anything. ( And it is easy to turn down the treble ).  Is it the better dynamic linearity?  Is it a clue that a 12W tube amplifier can sound as "big" as a 100W bi-polar?  Less IMD? Difference in how they behave at clipping vs SS? Higher noise floor that masks nasties?  Or a noise floor that is more constant and not pumping?

Besides Carver's work, also read David Manly and how increasing the grid isolation resister can make a tube sound more solid state.  

I think Benchmark might disagree with SS "missing" something. :)

Now as far as that "metallic" sound, I did find this as one of my easy showroom "NOs" when auditioning amps. A great test is a good classical guitar recording and if the bass strings sound metallic.  Very clear on some Julian Bream.  A Vocal like Joan Baez can show it up.   My MOSFET passed. Modified Hafler and B&K passed. Atoll and Hegel integrated passed. So does my new Rekkr and Vidar.   I thought it was more Bi-polar vs MOSFET, but some bi-polars' sail through too.  Some failing costing well into the ego bragging range so none of that "not expensive enough stuff". A $150 Schiit passes.  Speakers have a bigger influence and for some reason, I have never heard a hard dome I liked.  By measurements, they should be better, but I keep going back to paper woofers and silk domes. 

Chasing "live" is pointless as you are dealing with the last link of the chain and the sources we have are no where near live. No one has ever succeeded in recording a piano half way believable I have found. ( if anyone knows one, let me know)  If not in the source, we are not going to reproduce it.  Pleasurable is a better goal. 

 The closest to "live" I have ever heard was a solo bass being bowed, 2 mics, right into a Revox half-track. Not even any Dolby.  Played back in the same room through some Levenson and first generation B&W 801's.   Close.   The best we can do is hope not to screw up what the recording,  mixing, and mastering engineers did to it.

I was about to try another tube amp. Last time I listened to some and then built a few, my MOSFET was better in all respects. Things progress though. My desk I could easily use a 6 to 10W amp and those are "reachable"   Jumping to 50 or so on my main stereo is out of my price point. Then I got the Rekkr on the desk and darn is it good. 

What each of think is pleasurable varies.  Sound is real, hearing is our brain deciding what we think. It is not objective no matter how fervently some seem to think it is.  It is personal and neither I nor you can tell anyone what they like.