I agree with Herman "it's all in the application", both for speakers and amps. Particularly in the output transformers. I use a Viva Solista, which is a 2 man lift. Only 22 watts, but it seems to have the grip to drive Wilson Grand Slams. Alright that is an exageration, but it certainly has greater grip than my 50watt Lavardin IT. In terms of speakers and tubes, it seems to me that impedence is more important than sensitivity. A flat impedence not dipping below 6ohms seems more important than 95db sensitivity. Perhaps others will disagree.
Finally, I think there are differences between tubes, given an equally competent application. I can't speak for all tubes and it is not a new observation, 300B's have the mid range magic, 845's greater control at the frequency extremes, i prefer 845's.
Finally, I think there are differences between tubes, given an equally competent application. I can't speak for all tubes and it is not a new observation, 300B's have the mid range magic, 845's greater control at the frequency extremes, i prefer 845's.