Is there any truth to this question?

I like 'the amp of the month club'. Never joined, never will and couldn't pass the physical!

However, given 2 identical impedance measuring speakers....they will react very differently to the same amp based on::
1. Phase data for the speaker. Reactance kills
2. Amps ability to drive such reactive loads.

To your last point of 'how much power is required' please add speaker reactance. Just my opinion, but the 'low impedance' / 'low sensitivity' = bad load thing has been repeated so often that as wrong as it is, has become a form of truth.
A dozen or more posts back, somebody drug Harbeth into the discussion. Low sensitivity? yes, in general. But easily driven by a 50x2 tube amp. The Harbeth? generally low reactance. 'Tube friendly', perhaps.

FWIW, all other things being equal, a speaker that's capable of true live volume peaks would be better. With that said, my priorities and budget considerations would let me compromise on ultimate sheer live volume levels before other considerations. Still, for me an otherwise fine speaker like the Quad ESL's don't cut it. Though it really comes down to what the given room could accommodate, I would prefer that a speaker could at least cleanly produce about 100 dB volume peaks. I really don't think the occasional symphony crescendo is really going to do long term damage to ones ears, it's the sustained high stadium volume rock concert thing that causes long term hearing damage. Just having a system that can achieve a scaled to the room volume level of a live performance, without the worrying anticipation of oncoming distortion or even just strain, makes the listening so much more enjoyable.

OOps, clicked too soon again. I not convinced that a similar circuit producing less volume will always sound better that a scaled up version of the same circuit producing more power. Sure, I've heard the argument that it's harder to match more output devices. On the other hand, if those collective devices can maintain their maximum potential before strain longer, it's quite possible that the higher powered amp might sound better. Furthermore, in some Class AB amps, there is a given % of bias in Class A before sliding into Class B. Therefore, the same circuit with greater power output can maintain the often preferred Class A bias longer. ...And all this with less of the worrisome anticipation of strain or even worse clipping. I don't think there is a hard and fast rule here. IME, it depends on the line of amplifiers being considered. The sweet spot in a line of amps can be at the low, middle or high output. Heck, sometimes samples to samples might vary. The application is the most important concern. IME, I'd rather have a little too much power (awarding a generous grace period if you will), rather than not enough.

Digepix,

I hardly think that success with the RM 10 goes against common wisdom, at least with respect to the tube crowd. Thirty-five watts is plenty of power for the majority of speakers on the market, as long as one is not playing the speakers at extremely high volume in a very large room. There are also those that think that deep, tight bass is the be-all-and-end-all of musical reproduction and those people, too, might find anything less than 200 watts to be inadequate. The rest of the crowd really don't need that much power.

I am not surprised that you like the sound of the RM 10. A good El 84 amp will have the kind of clarity and punchy sound that would complement something like Vandersteen 2s and 3s. Many of the best bargain tube amps use that tube.

You should ignore "common wisdom" of the high-powered crowd and go with your own experience-- you seem to have clear preferences that are certainly NOT inconsistent with what a lot of others hear. By acknowledging that low-power gear CAN work with your Vandersteens, you expand the possible choices that could deliver satisfaction, at perhaps a substantial savings.

Just a handful of suggestions: Atmasphere's 30 watt OTL, tube amps from Audiospace (Hong Kong), tube amps from Synthesis (Italy), tube amps from DeHavilland, solid state First Watt J2 (25 watts).

"There are also those that think that deep, tight bass is the be-all-and-end-all of musical reproduction and those people, too, might find anything less than 200 watts to be inadequate. The rest of the crowd really don't need that much power."

Deep tight bass is very important to me but not the be-all-end-all. That's just one piece of the puzzle. But to get that one right, yes in many cases beefy amplification is exactly what is needed to get that right, but I find the rest need not suffer as a result and in fact can also still be top notch. It all depends....