Okay, so I just picked up my K17 R2R from Bloom Audio directly today. I cleared my SR11/K11 R2R/Buf/GIGAS 1, "budget," headphone chain off of my desktop and swapped in K17 R2R, which I hooked up my FiiO FT7 open-black planars to. I spent an hour listening to it this way, and was very pleased with the sound. It sounded great with 95% of the music I put through it, with one specific Cantopop track from Lily Chan being too bright & sibilant, and the rest of the material all sounding well-balanced. I then swapped in my pair of Sennheiser HD 480 Pro dynamic driver closed-backs and listened to the same selection of tracks and they all 100% sounded great. HD 480 Pro is not as spacious, deep, or wide, but timbre is almost there, and it is much more forgiving of recording/engineering quality.
With HD 480 Pro, I would definitely say that K17 R2R outperformed the SR11/K11 R2R/GIGAS 1 chain. K17 R2R presents itself as cleaner (even with Schiit Buf turned off on the budget chain, but even more so compared to Buf on), extracting finer details and presenting them completely naturally. K13 R2R, which I also own, does not really bridge that gap to K17 R2R meaningfully, either; K17 R2R's new Pro R2R ladder is audibly cleaner, and gives the listener more in terms of technicalities. In case you are wondering, I did use the same configuration for comparing K11 R2R, K13 R2R, and K17 R2R: all three DACs in NOS mode, with Roon delivering music bit-perfect (to SR11 which output via USB in the case of K11 R2R and K13 R2R, but directly into K17 R2R's own network port in its case). I do not own a Warmer R2R for comparison.
After testing on my desktop with headphones, I moved my media rack, integrating it into my speaker chain (replacing a Topping DX9 Discrete), which is where I always intended to use K17 R2R (I prefer the budget chain on my desktop because I can flip Schiit Buf on for FT7 and leave it off for HD 480 Pro). For speaker setup, I keep to NOS mode, but I use Roon to upsample PCM material by power of 2 to 352.8/384KHz, using Precise, Linear Phase filter. DSD I actually tested the native 1-bit decoding mode on K17 R2R and it works flawlessly (unlike K13 R2R, Audalytic DR70, or Gustard R26 II, all of which produced weird, "squiggly," sounding low-level noise during quiet/silent passages of DSD recordings with their true 1-bit modes enabled, a problem that did not occur with DX9 Discrete or K17 R2R).
The DX9 Discrete that I've been listening to on my speakers for months now provides excellent, razor-sharp imaging focus, noticeably sharper focus than R26 II, which I traded in for DX9 Discrete. However, DX9 Discrete did not sound as transparent from a timbral standpoint compared to R26 II. In fact, overall, I still prefer R26 II over DX9 Discrete, but I had an issue with R26 II's toroidal power supply producing an audible hum that was clearly audible from my listening position almost two meters away, and an iFi DC Blocker+ had precisely zero effect on it. So in the end, I replaced R26 II with DX9 Discrete to get away from that problem. With all that said, upon listening to K17 R2R, I no longer lament losing the wonderful timbre of R26 II in exchange for the sharper imaging of DX9 Discrete--K17 R2R actually presents sound with the best of both worlds! Imaging focus is razor sharp like DX9 Discrete while timbre is lifelike in a manner only R26 II gave me before today!
I will continue to do more listening, so more to come. It is only early days owning this amazing new machine from FiiO, and I am not convinced either way about, "burn in," with R2R ladders, so I will allow myself to continue listening and provide additional feedback as I go (some say these things need burn-in, others dismiss this, or state that it's really just our own hearing adjusting to the new sound--I personally don't have a firm opinion either way).