Autoformer Volume Control (AVC) Before or After Active Stage?

I would eliminate the buffer. It would only be useful if your source had a high output impedance and you needed to use a really long interconnect.

I tried it without the buffer first and I will continue to listen both with and without.  I owned the icOn Pro4 (balanced version) AVC preamp for awhile (link to review) and, for whatever reason, I didn't like the sound of the Pro4 with the buffer.  

In the case of this Hattor ARP, the buffer does change the sound somewhat but, unlike the icOn Pro4 where I simply didn't like how it sounded with the buffer, the Hattor ARP it sounds pretty good both with and without, just different.  I will probably be able to describe it better after I spend more time but, for now, the buffer seems to add a bit of body/fullness to the sound without a noticeable penalty.

I can't speak to your specific components, but I have transformer volume control with my active tube pre, so essentially my active is the buffer. Seems to me putting the buffer in front of autoformers defeats the purpose of the buffer, the passive negates specific voicing of the buffer. You mention buffer adds a bit of body/fullness to sound, this what I'd expect having tried passive pre's in the past. Never tried autoformer based one, but just didn't supply the meat on the bones I need to feel like real live flesh and blood performers in room.

Is this the same as what anti cable auto former?

@jayctoy - To your question, probably yes. An autoformer is basically a transformer with a single winding, while ordinary transformers have separate primary (input) and secondary (output) windings.  

The Anticable ZERO-Autoformers come as a stereo pair of Autoformers which increase the impedance of a pair of speakers, so they probably only have one tap per device, vs. an Autoformer volume control which has multiple taps. Should be generally the same concept and and function however.

BTW, Intact Audio (Dave Slagle) has an interesting write-up on autoformer volume controls. (link) 

Been doing some A/B’ing and pretty sure that, with my gear, the AVC preamp/unity-gain buffer combination sounds best when the AVC preamp proceeds the buffer.  With the AVC preamp first, the sound seems more coherent with fuller bass, richer tonal qualities, and smoother treble.  This may be a function of the sound quality of the buffer having a greater influence when it is behind the AVCs in the chain.

Next, I will try and determine whether the AVC preamp sounds better on its own or along with the buffer.  Once I figure that out, I will compare whichever result I like best with the resister-based preamp/buffer combination that I was previously using.