I am sure there are plenty of folks building the design, not so sure about tweaking it. Regardless, this thread has been pretty quiet as of late. Looking back, the Rev A is a little over a year old, certainly not ancient, but, obviously not FOTM any more.
As for the noise measure, I have not seen anyone post any measures of the rev A. Personally, I have not objectively measured it, but, subjectively, it seems quite black to me. As of late, that can be a dangerous statement, but, my measurement tools are fairly primitive and would probably mislead rather than inform. I may try to change that situation, just not high on the priority list as of late.
That said, I think the noise floor is going to be impacted by the build techniques (power supply locations) as well as the overall gain setting of the amp and the source being employed. The nice thing about the rev a is the power supplies can be detached for a two case build if so desired.
I have Grados, so, if you can provide a silent waveform (which I assume is created to be a binary zero representation of silence), I will be more than happy to give it a subjective listen.
As for the cathode bias point, I am not sure why Alex picked what he picked, but, I am sure there was rationale behind the choice. I think it would be most cool if you experimented a bit in that area and shared your results.