what is it that makes one speaker sound better on ss and another on tubes? Is this an experience item or are there specs I can look at?
Maybe you should look here first:
http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.phpIn a nutshell tubes drive speakers differently than transistors tend to, although you can make them do it if you add enough feedback. The problem is that when you do this, you will also rob them of the music. IOW, its not so much a transistor/tubes debate as it is whether or not making an amplifier into a Voltage Source is a good thing or not.
To this end I don't agree with Unsound, as the research that has been done in the last 45 years points to the fact that the human ear is very sensitive to the use of feedback in an amplifier, and also that it hears harmonic distortion as tonality. Another way to putting this is that you will have a very difficult time to get the equipment to sound like music and run feedback at the same time.
The B&Ws require that the amplifier be a constant voltage source which is why they don't work so well with tubes.
So if you want tubes, you *have* to find a speaker that works with them. If you go with the speaker first, you may be forced into using a transistor amp. Since most transistor amps use a fair amount of feedback, its nearly impossible to get such a combination to sound like real music- at best it will sound like a good hifi. Its that last nuanced difference that brings home the bacon!
Now you could try using transistor amps that have no feedback; there are a few around like the Pass Labs and Ayre. The problem is that transistors have non-linear capacitive aspects in the junctions of the device itself. This contributes to odd-ordered harmonics- the very thing that the ear uses to sort out sound pressure (volume of a sound).
Another way to put this is that the more the equipment obeys human perceptual/hearing rules, the more it will sound like real music. In a nutshell its easier to do that with tubes than with transistors- I am not saying that its impossible with transistors, just that its several orders of magnitude more difficult.