4 amplifiers to drive 1 pair of speakers?

thegreenman, excellent job of thinking creatively in terms of system setup! Most people do not have the vision to see such potential. It is through exploration of options that would not necessarily be considered that some very cool things can happen. Note well: multiplicity of amps does not equate with superior results. Many factors go into the result, and simple higher quantity of amp channels is no guarantee of superior sound. 

You have been given superlative advice from seasoned veterans that it may not be an ideal setup. In general, over many years of building hundreds of systems, it has not been the quantity of amp channels, but the quality, i.e. not only the build quality and preference for SS or Tube, but Watts and current delivery, that has been THE most important aspect. 

I have many times tried unusual configurations such as splitting the pre output in order to do additional channels, and nearly always a simply superior amp yields a much preferable result to use of several amps. There is a HUGE difference in systems set up with even one stereo amp and bi-wiring versus multiplication of lesser amps, or additional amp channels. That may sound counter-intuitive to you, but you need to trust me and others who are guiding you.  :) 

Listen to the old warriors; they know whereof they speak.  :) Personally, I would not dream of using so little power on any nearly any speaker, regardless of its efficiency. I have speakers above 90dB sensitivity, and I drive them with hundreds of Watts. I would not wish to drop down in power, because even they would sound relatively anemic in comparison. You may disagree now, but that is lack of experience. You are absolutely wasting those speakers with 18Wpc.  :(  You are getting nothing close to what they could do, and with zero loss of beauty of tubes.  

You will get a fresh take on amps in my upcoming article at Dagogo.com in regard to the Legacy Audio i.V4 Ultra Amplifier. The world is changing, and in this case, much for the better!  

Now, there will come along someone who will suggest i have it all wrong, 
that even the 18Wpc is "plenty" to drive the speakers. True. Is it superior, the best you can do? No, not even close, imo. Of course, opinions will vary, and you must choose your authority - and get your results.  :) 

thegreenman, you only see what I want you to see...  ;) 
(Quite mysterious, eh?) 

There are certain ways using multiple channels may (for the community's sake, notice the word "may") sound better than a stereo amp or monos. 
Do not be overly impressed by rigs with many amps; it is not a sure indication of superior sound quality. In several respects, a more streamlined rig is preferred. It is far easier to screw up the result when multiplying functions, and it is far harder to dial in a rig to perceived perfection as well. 

If you would like to see the list of amps I have reviewed, check my reviewer profile at Dagogo.com under the "Staff" tap at the top. 

I just sent back some mono amps, so at the moment I have the Kinki Studio EX-M1+ Integrated Amp, the Redgum Audio Articulata Integrated Amp,  and the Legacy i.V4 Ultra Amplifiers here. I have another top secret on coming soon. Sorry, I do not typically reveal the identity of review items far in advance of the article. I can tell you this; it will be a stereo amp and about 100Wpc. I suspect it would sound very good with the Legacy Whisper DSW Clarity Edition speakers you mention. 

To give you some idea of how vastly amplification can range in terms of performance, the Redgum integrated amp has bested several other SS stereo and mono amps. It has terrific ability to push less efficient speakers such as electrostatic speakers. Amazing rigs can be built with monos, stereo, integrated, and multi-channels. 

There is often something lost in the effort to push toward the lower power, higher efficiency end of the spectrum. When you have heard both ends many times, you understand that. A person has to make a choice between the set of attributes most desired, and you usually cannot have both. 

thegreenman, The genres of speakers that can be driven with low powered tube amps is unacceptably narrow to me. I do not wish to limit my experiences based on the inability of an amp to drive different genres of speakers well/properly. Some accept that limitation, but I choose not to.