I replaced a Sonic Frontiers Power 2 (Svetlana KT-88's, Jan Philips 6922's) with the VS.1 MKII and find the midrange is not too much different from that of the SF amp, VTL amps, and other large contemporary design push pull tube amps. The bass is definitely better. The treble is some of the least fatiguing I have heard with a solid state power amp. The soundstage dimensionality is good -comparable to the SF but not quite as good as my 300B and 2A3 SET amps. My Maggie 3.6's, which sound harsh with some solid state amps are very happy with this one. I'm using Tungsram E88CC's in the preamp section.
On a separate topic, I exchanged emails with Daniel Khesin (DK) about the class A design of the power section. I asked how a class A can run so cool, and he replied that The VS-1 Mk. 2 uses proprietary circuitry (which they obviously don't want to say too much about to their competitors).
I also asked about the power meters which are marked in watts but actually measure the input signal before the volume pot. He replied that they were evaluating the available uV meters and found this very attractive and high quality one that's marked in watts, and changing the tooling to reflect uV would have added considerably to the cost without improving the quality, so they decided to incorporate it into the design without change.
I mentioned that after hearing the DK amp in my system I plan to sell the SF Power 2, and he commented that one customer is replacing Halcros with a VS.1 MK2. Whether this is marketing hype or not, I'm very impressed with this amp. Definitely a keeper.