I have heard a lot of the preamps that you are either considering or which have been referenced above. I have also included below some models which are relatively close to ones which you were considering or referenced above:
BAT VK-51 SE
VTL 7.1
VAC Renaissance
Ayre K-1(x)
Lamm L-1
Aesthetix Callisto
Of course, I heard these, for the most part, at different times, often with different equipment and different music. Most were heard side-by-side in A/B situations with at least one other mentioned here. In one or two cases, a unit was heard with comparison to something not listed, like the Hovland HP-100.
Of these listed above, the only one which I thought was outstanding in a whole lot of ways was the Ayre. It is smooth. It spreads the instruments out well in space. It reproduces detail, but in a natural way. It is just a little cooler than natural, in my opinion. The dynamics are a little understated. The phono section is superb.
To the list, I would add/reinforce Convergent Audio Technology Ultimate and First Sound Presence Audio Deluxe Mk II. I would also throw in the Herron. These first two sound quite different and do different things exceptionally well. CAT is known for smooth-as-silk, effortless presentation, incredibly solid and deep bass, stunning dynamics, sweet, mellow, lush midrange, great soundstage. Maybe not the best in EVERY category, but way up there in just about all and when considered as a whole, a very difficult product to beat. First Sound is stunning to me for its midrange transparency. There just seems to be nothing between you and the music in that range. Although it is quite neutral, you wouldn't call it that because vocals almost seem live. You have sensation of very low noise floor. Excellent soundstaging. Bass is good, but in my system, not as deep as CAT. Dynamics are good, but not as good as CAT. Transparency of the First Sound is like nothing that I have ever heard, including the CAT.
There are probably others, and I, just as all the others who have posted on this thread, can't tell you what to buy, but you can't say that you have surveyed the top preamp terrain if you haven't heard these two ... and the Herron.
