Take a look at this topic: https://dynacotubeaudio.forumotion.com/t2754-hooking-up-6ohm-speakers-into-an-m-125
I wouldn't worry about it, most people just want stuff to work and sound good and don't want to get lost in the electrical engineering weeds so manufactures probably choose to keep it simple and not potential customers by including too much ancillary information in their manuals.
I run an older pair of B&W's, CDM7NT's. I'm curious on your impressions of your B&W's and your reasons for upgrading. I caught that bug a year ago but never upgraded. Couldn't justify the change.
I am fortunate in that I have a dedicated room that "with a little help from my friends" I completed in 2001...a year and a half in the making.
I have owned my 804's since 2007 and have been happy with them. At the time when the diamonds came out in both the 803/804 I frankly could not afford them so ultimalty they were put on the back burner.
The 804's serve me well in both formats.
I am new to tubes thanks to a friend I had met on the Emotiva Forum who introduced me to Bob Latino's amplifiers. My current 2channel system reluctantly I can NOT lay claim to the thought process that was put into it. At best I had little genuine thought about what products I wanted in a 2channel stereo system. I was listening to my music thru my Outlaw990/7700 combo which was adequate but way below my expectations. The Outlaw work flawlessly in my HT setup and continues to give me enjoyment.
I was disappointed in my 2channel to the point I purchased 2XPA1's second generation after reading how much better to have addition HEADROOM with these amplifiers.
Again I was disappointed. Thru the Emo forum I met Bill Gratrix. Bill graciously invited me to his home to give a listen two his system having the m125's.
In short I was in awe of how dynamic and transparent his system sounded to me. Not loud, no need for EXTRA headroom Bill's system was as if the artist presence was in the room.
I was convinced that tubes were the answer. The warmth that tubes give to well record music is a big difference than SS.
In short I sold some of my equipment and invested in Bill's ideas who from my initial meeting trusted in his experience and i liked what he was telling me in how to attain a quality 2channel stereo system.
The 804's sound great and at this point I am not sure about either the 803d/804d...BUT I am still considering a change for more transparency in a speaker. I feel the 804d has it, the 803d has it both at different levels. I am going to a demonstration this week to listen to both speakers.
I don't think you would disagree with the performance level of the diamond series assuming you have heard them.
Even with the demo pricing the B&W's are not cheap but many would consider them a bargain. I have read that for resale value theB&W's are one of the top three speakers on the market.now here's what I find interesting. Yesterday I was at an audio show in Rockville Md and I had a chance to listen to Salk speakers.
Jim Salk had a prototype speaker there in white, with a ribbon tweeter, mid-range and two woofers. The speaker is not on his web site or is he advertising.
I asked him if I could hear them and I can tell you that new Salk was in the mid-range clear as a bell and one of the most transparent speakers I have heard.
My friend who had in the last year purchased a pair of Focal speakers for $5000.00 was blown away and wished he heard the Salk before buying his Focal.
Price of these beauties..$3000.00 with any finish.
So now I am considering the Salk with a gauranteed refund if the speakers do not work in my system or consideration of another Salk model.
This is my reasoning, perhaps insane but it's an honest account of my travels on this road and where I am in the journey.