Heat 
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That’s still a valid exercise, albeit you need to get your hands on a unit which is physically up to the task of driving the speakers…
…and realise that: circuit topology (rather like valve types) is just one small part of the story.
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Yep.
You’d normally hope that Class A operation subtracted something (ie the effects of switching distortion) but you still have to be sure that the amp isn’t being operated outside its specified envelope. I suspect that this kind of amp into the small Celans probably is being challenged at LF where the impedance of the speaker likely dips a little.
Late to the party, sorry, but this. I was told to make my Triangles (91db) really sing I’d be best sticking 25w of valve class a up them.
This was from a dealerscum who didn’t have anything like that to sell me, so suspect it’s not total bullshit.
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I used Triangles at Scalford some years ago with a small 12 watt amp that powered them very well.
I use a pair of 16W Class A Rank Concept Monos with my 90 dB ARTs. They have been very decent up to now, although a little more oomph would be nice.
Over x2 and x3 the power Mike was trying. The 25w figure was just what was suggested to me.
Olans system certainly sounds great to me.
I remember being pinned to the sofa by Doms (North West Analogue) system which iirc was 12w but through some really efficient home made (but didn’t look it) speaks. Really changed my viewpoint on how many watts are required.
A 90dB/1W speaker is about 0.6% efficiency, so 99.4% of your amplifier’s power is converted to heat.
A 105dB/1W speaker is 20% efficient.
Think about how much of your 5W makes it into actually moving air in each scenario.
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They have a damping factor of 3, into 8 ohms 
I’m beginning to suspect that, just maybe, I was a little optimistic with the whole 5W / 90dB / small room thing.
So, I have 2 options - find an affordable Class A power amp that will drive the Celans, or get my Class D amp spruced up.
Anybody know where I can get my lovely 200W Class D fitted into a nicer box ?
I think that 5W may be enough, but it has to be 5W that can drive real speakers. I reckon the Pass is there to drive things like Lowthers at 96dB/W and dead easy to drive.
That said, you seem to have proved that you like your class D amp, so just box that up and enjoy it, and maybe get a Croft Micro pre if you want to spend some money.
Wtf does that even mean? 5W is 5W.
A low output impedance
What has that got to do with power?
Usher R.1.5 Class A Stereo Power Amplifier
Ok: “a 5w amp may be enough, but it has to be one that can drive real speakers” - is that better?
Honestly…
Not really, because it makes no sense.
So what you actually mean is a 5W amp that is capable of supplying more than 5W. So, err… a 5W amp isn’t enough.
Ohms law is pretty definitive on this stuff.
My assumption is that it’s not clipping. I may be wrong - he may just be playing it too loud for the amp.
You need to understand the relationship between power, current, voltage and resistance.
https://www.electronics-tutorials.ws/dccircuits/dcp_2.html
Things like “real 5W” are audiophile bullshit.