Some high efficiency speakers tend to be tipped up in the presence region from 1k - 4k. I built a pair of bass reflex boxes using Fostex 206E's that exhibit this characteristic. They are great speakers with intimate fare but get boring (into your skull) with hotter music.
With the solid plate EML's, the Yamamoto is not the prototypical SET amp. It isn't particularly lush or euphonic. It isn't syrupy or mellow either. Aside from the obvious efficiency concerns remember this pair won't mellow speakers.
From what I've read, the mesh plates will relax the presentation and NOS tubes further so. I don't have experience with these so won't comment.
That said, the solid plates in this amp are really spectacular. They have edge and grit where the music calls on it while still filling in the breath and space of real performers in live spaces.
My setup with the Def. Pro's lets me change the XO between the sub array and mains so when I really want to crank, the 2 watts can still do it without complaint. It's really something.
