Hi Fred,

Great setup!  Love the equipment and aesthetics.  I either own or have heard every piece of equipment you have - turntables excluded.  Nice job acquiring the quality components that you have.  

If this was my system, I would connect the Node 2 via digital coax rather than the optical.  There is plenty of data in the wild regarding the superiority of digital coax over optical.  Secondly, I would remove the pills, get used to the sound, then insert them at various points for comparison.  You may find that they detract more than add - but I am definitely more of a "purist" when it comes to handling the signal once from when it leaves the source to when it reaches the speakers.  The ZBIT fed by the XLR outs on the Oppo 205 going into your tube gear should not need the influence/manipulation of the Pills.  I don't think they were designed to be implemented as you intend, but Steve is the authority and probably best to shoot him an email with this very question.  Sure they will "work," but again, they are going to be surrounded by equipment that really won't need anything it was designed to offer.  More isn't always better - and quite often it is worse.  The Pills are more of a fix for a weak link component and where you propose placing it doesn't really fit the model. Again, this is Steve territory.

Not sure what it would take, but I would consider getting your ZROCK upgraded to the v2.  The latest rendition can handle 15(?) volts from what I recall reading in one of Lon's posts about this very subject.  I know, more money, and more wait, but not being hamstrung by voltage limitations is a beautiful thing and something that could be a game changer with the equipment you have.  Or, you keep the attenuator at a point that doesn't surpass the 4 volt limit and just ride the gain with your CSP3 and ZMA combo.  I don't believe you could go wrong either way, but personally I hate limitations as it always leaves me wondering, what if?

Your last question... Its a doozy and is one of those "Pandora's Box"/"Can of Worms" questions.  This has been hotly debated across countless forums and still remains unsettled.  The main focal point of this quagmire is jitter.  The proponents of audiophile-grade digital equipment proclaim jitter matters when it comes to audio data.  I happen to agree, based on my experience.  I just spent $1500 on an AQVOX audiophile switch and ethernet cabling and am not disappointed by the purchase whatsoever.  I have also invested thousands into my PS Audio Directstream DAC which natively streams and fully unfolds MQA Tidal.  So, eliminating any and all weak links in my digital chain is worth it to me. Anyway, if you have a full day to kill, do some targeted searches, pinpointing "the affect of jitter on digital audio sound quality."  There should be enough there to make your eyes bleed.  My advice, get some loaner high-end, audiophile-grade digital cables from The Cable Company's "Cable Library" (https://www.thecableco.com/content.aspx?iid=5777).  If you like them, you buy them.  If not, send them back, no muss.. no fuss.  Don't let my opinion convince you to spend money that may not provide any audible improvement in your system. And don't let any naysayer dissuade you from implementing this digital cabling which could very well improve the sound quality in your digital playback system.

Good luck!  BTW, these are all wonderful and exciting "problems" you are facing here.  It IS the journey!