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Hi asx77,
Thank you for such a good starting point to begin my research for finding a tube amp solution.  This would be my first non ss amp as well and I definitely need to listen critically before I purchase one. Its difficult to comprehend that some value amps can function and sound well with less wattage when the general consensus is the more watts your amp has the better the amp will sound. I heard a quote from Nelson Pass the amp designer who said "The first watt is the most important watt".
I am in northern California and I will investigate if there are upcoming audio shows in my area although its been difficult in the last few years with covid closing many events and sadly specialty audio stores dwindling.  From what I have read the recommend amp power for B & W's is between 30W - 120W into 8Ω .  The forums that I have searched for answers seem to favor the ss approach for B&W's but that may only to their limit experience with value amplification. I will send an email to B&W as I have heard they are quite responsive. Once again my thanks and gratitude for all your suggestions and pointing me in the right direction. 

My speakers are rated about the same, 30-150w without clipping. I think this is typically just a guide for consumers to allow them to purchase amps that will allow the speakers to reach their max volume without clipping. With your range (30w-120w) that’s only a difference of about 6db.

I don’t think Nelson Pass was the first to say the first watt is the most important but he clearly believes in it.

 If you use this calculator (see link) it will give you an approximate idea of how many watts you need. I typically listen at an average level of around 75db so using the calculator I apparently need less than a 0.15 Watt!! If 75db is in the middle of the dynamic range of music then for peaks I need say 90db which takes me to 4 watts although another school of thought (I think maybe Bob Carver) says if your average is 0.15 then the peaks will need x10 that value. Obviously this calculator doesn’t take room size and materials into consideration but you get the point.  www.hometheaterengineering.com/splcalculator.html.


Watts are important to avoid clipping of transients. But I understand they’re more important for solid state amps that clip in a very noticeable and unpleasant way. It’s less important with valves because they ‘soft clip’ but tbh I’m not entirely sure how far beyond their rated power this actually starts to happen (ref earlier post where I said I was told by an OEM the power rating is relative to 1% thd) so perhaps clipping occurs on some designs some way beyond this.  Edit: Note my amp's tap is designed for 6 Ohms nominal speaker load and it's output is therefore rated for this nominal load but designed to cover the swing from 2-10 Ohms easily. My OEM recently told me that if my amp produces 1% THD (mainly 2nd order harmonics) at 20W into 4 Ohms, they could still go higher say upto 30W into 4 Ohms but produce 2-3% distortion.