One more consideration about location of both A16 unit (2U as I have) and your own separate headphone stand (Stax wood stand for my SR-009) is the additional thin cable for the A16 head-tracker that is affixed to the headphone band. This is one of the complications of using a wired-powered HT (rather than the rechargeable battery powered HT as with the A8, which thus had no cable considerations).
And don't forget about the secondary thin cable going from the A16 to the set-top unit (for the head tracker). It needs to be located above the center of the top edge of the TV with its own long cable run to the A16.
And then of course there is the headphone amp itself (Stax SRM-007tII for me) which also has to be connected to the headphones, also by its own long cable run. This is effected by your viewing/listening location relative to both the TV and wherever you've got the headphone amp. Not to mention that the headphone amp must be connected either to the A16 or to an external DAC, so all of this must also be in the same vicinity for cabling.
So it's a real cable management challenge when you add in the interconnect requirements of potentially one or more source devices (going into either the A16 or the AVR if you have one), possibly/probably an AVR, and also a connected TV. Quite the challenge.
My own "solution" was to place the A16-2U on a shelf in the "entertainment rack", where all the other "source devices" and AVR already were located. So HDMI interconnects were conveniently short and standard (and all hidden from sight BEHIND the rack and equipment), with four sources going HDMI into the A16 inputs, and the A16 output feeding HDMI into the AVR, and the AVR eARC-enabled output feeding 20ft. HDMI (fiber optic) into the TV. The A16 also has an optical-out connection to my external DAC which feeds XLR to the Stax headphone tube amp (on the top surface of the rack).
I already had a 16ft Stax silver extension cable added to the primary 8ft cable that is on the SR-009 itself, in order to reach from my listening location opposite the TV to the headphone amp located on top of the equipment rack. Fortunately, Smyth includes both a primary and extension cable for the HT. So for me there was absolutely no issue with the length of this HT cable going from the headband of my SR-009 to the A16 itself. Also, Smyth provides a number "black plastic clips" that can be used (quite successfully, spaced out over the full cable length) to secure the thin HT cable to the side edge of the [extended 24ft] 6-strand flat Stax headphone cable that makes the identical run from my head over to the equipment rack where the headphone amp lives.
As-is, this cabling and device/equipment location arrangement supports my "normal viewing/listening" habits. I can listen to SOUND FROM ANY SOURCE either (a) multi-channel through he headphones connected to the A16, or (b) to 2 stereo speakers connected to the AVR. When using the 2.0 stereo speakers it's fed either from a genuine 2-channel source, or from any multi-channel source downmixed to 2.0 stereo by either the A16 (for multi-channel streaming sources) or the AVR (for eARC from apps running on the TV), or in fact by my Oppo 203 (from discs, or from DD5.1 audio from HDTV). This cabling also supports ARC/eARC audio from the TV fed to the AVR for listening to sound through the 2.0 speakers, if that's what I want to do.
Note #1: If I want to use a streaming source app running on my LG C9, and feed audio from the TV via ARC/eARC to the A16 for listening through headphones, I must physically move the HDMI cable normally running from the AVR to feed video to the TV, from the HDMI-out of the AVR over to HDMI-out of the A16. The AVR is now no longer involved, and can be powered off. But if listening to ARC/eARC audio from the TV to AVR and 2.0 speakers is acceptable I can just leave the HDMI cable as-is, going from HDMI-out of the AVR to the TV. Then the A16 is not involved and can be powered off.
Note #2: I have an Oppo 203, used to play discs. Its HDMI1-out (video only) goes to an HDMI input on the AVR, and from the AVR's HDMI-out on to the TV. HDMI2-out (bitstream multi-channel audio only) of the Oppo goes to an HDMI input on the A16 (for decoding/processing and play through optically connected external DAC/amp/headphones).
Note #3: I have a Yamaha RX-A1080 AVR which has 8 HDMI inputs, of which I use two: (1) from Oppo 203 (for video only, from disk playback and external HDMI input for cable HDTV), and (2) from A16 (for the three A/V streaming source devices feeding into the A16, i.e. Roku Ultra, ATV4K, and Shield Tube).
Note #4: I have a DBX 14/10 EQ which supports two analog 2.0 stereo (RCA) inputs, that I use in order to provide 14-band tone control to the 2.0 stereo speaker sound whenever the AVR and speakers are used to listen. One input to the EQ comes from the L/R channels of the 8-channel "preamp analog outputs" of the Oppo. I have the analog audio output of the Oppo set to "downmix to 2.0 stereo" so that if I want to listen to multi-channel source (e.g. DD5.1 on HDTV going into external HDMI of the Oppo) through 2.0 speakers the downmixing to 2.0 stereo occurs in the Oppo, which feeds its 2.0 output into the EQ, which feeds its tone-controlled 2.0 output into the AVR (via analog, associated with HDMI video from the Oppo through the "scene" setup on the AVR), and then out to the speakers. ==> So multi-channel A/V disc/HDTV source from the Oppo producing either (a) multi-channel audio from A16 and DAC/amp/headphones, or (b) 2.0 channel tone controlled audio from EQ/AVR/speakers.
Note #5: If I want to listen to 2.0 stereo speaker sound for a streaming source going into the A16, the downmixing from multi-channel to "plain" 2.0 stereo now occurs in the A16 for feeding to the optical output (with SVS specifically disabled!). The optical output goes to the external DAC, whose own RCA outputs now feed the second RCA input of the DBX EQ so that, again, 14-band tone control can be applied. The tone-controlled audio output of the EQ again feeds an analog audio input of the AVR which is again paired with the A16 HDMI video input in the AVR's "scene" configuration. ==> So any multi-channel streaming A/V source into the A16 producing either (a) multi-channel audio from DAC/amp/headphones, or (b) 2.0 channel tone-controlled audio from DAC/EQ/AVR/speakers.
