I finally got through to HiFiMan today - day 4! They were incredibly helpful and friendly and so we will begin the RMA process. Thank you to everyone including AnakChan and Hifiheaven for helping out on this - much appreciated!
Regarding the recent headphone / amp pairing discussion, the V281, it is a fantastic amp. It is the only amp out of half a dozen I own / have tried, that drove my LCD i4s to my satisfaction (I find them the hardest transducer I've ever owned to find the right amp for). The i4s, IMO, have a forward midrange that can get 'shouty' especially with female vocals (YMMV - this may be due to anomalies with my inner ear) but the V281 seems to interact with the i4s in the most effortless way making the sound flow as naturally as possible out of them. I also liked the Naim Headline 2 with a Teddy Pardo power supply, but the V281 offers more resolution. But IMO the V281 only drives the Susvaras satisfactorily. There are no lifelike dynamic swings, there is no 'wow' factor, soundstage is not the widest, and on and on... There is resolution, there is bass and treble, but you feel like there is a lot missing - especially an emotional connection to the music... The XA30.5 I was able to try before I purchased the Susvaras had all of these elements in spades. I wish I could add more adjectives or describe it better, but it is the type of thing that you know you have right when you have it right. And, this is where synergy becomes important and where science intersects with the dark arts
Regarding science, a lot of it has to do with current. Planars have always been known for being current hogs. It is a rule of thumb with Magnepan planar speakers require massively high current amps. Wattage is a factor but not nearly as important as current. I've seen this first hand with many pairs of Maggies I've owned over the years. A 28 wpc 845 tube SET amp with massive current capabilities drove Maggies very well while similarly wattage amps struggled. I think the same is true for Susvara's. Use Pass Labs as an example (again!), the HPA-1 and the XA 30 watt amps (.5 / .8) all put out ~2.5 wpc at 60 ohms. It's unanimous that the HPA-1 struggles and the .5 / .8's sing. The dark arts part of the equation comes into play because there are other factors (scientific and likely non-scientific) that create and hinder synergies. Surely other factors come into play re: Susvara and V281. I hope this helps explain my perspective a little bit better...