@kairosman I'm using custom cabling (interconnects, power cords, USB cable) by the same guy who modified my x20pro... it's very good stuff. His friends in the N.J. Audio Society say it compares favorably to multiple-$1000 commercial stuff, but I've never heard anything other than Igor's cable except for low-end Cardas and such. The "slow" filter sounded best for detail and microdynamics. I didn't like NOS much.
When I refer to imaging I'm actually talking not about my headphones but about my humble speakers... Spendor S3/5. They have great imaging with my modified Gustard x20pro, in terms of the spooky realistic sense that you can face the direct source of sound and pinpoint its location in space. With the R26 the images tend to exist in either left, center, or right, and not be stable. The sizzle on a violin might seem to come from a different place than the body of it.
The headspace of the R26, with headphones, is decent. I like a sense of open sound when I'm using headphones, i.e. that the boundaries of my head aren't precisely limited, and I get that with the R26.
What my R26 does really well is soft music, like the fade to silence (or fade up from silence) of a reed instrument. But in general it seems too soft in the top octave.. it requires careful attention to pick up on details. It doesn't grab me like the x20pro.
Right now, it's playing pink noise through my relatively new LCD-X, so we'll see how they both sound in a few days when it reaches 200 hours.