Paul,
As I noted in my post, I've never gone the really low power output route, so I wasn't commenting on any of the 45 tube designs. OTOH, you mentioned the 211 tube as well. I use this as the default tube in my Cary 805s specifically because the slightly "darker" top end (vs. the 845 output tube alternative) emphasizes the warmer tonal balance of the amp. When the 845 is in service in the Cary, it, too, is warmer/lusher than most amps I've used, but closer to neutral.
I'm sure that tonal balance of most SET amps varies with the impedence curve of the speaker being used, so my observations are qualified by that fact. In actual use, my SET amps have produced pretty consistent results, regardless of the speaker; deep bass is diminished, mid-bass performance is strong, midrange lovely, highs are airy but a bit rolled off. (To be honest, I no longer hear the roll off at the high end - probably one more 50th birthday gift). Dynamics are surprising, almost always exceeding expectations for the power output. However, IME (which -to be clear-excludes the 45 and similar very low output designs), SETs definitely tend to be warm and lush.
