So I got a pair of those HiFiMan Sundara today since they were so cheap. I had been considering buying the Arya Organics, but was reluctant to due not being to hear them prior to the buy. I've been switching back and forth between two other headsets for the past hour or so, listening to the same songs at the same volume levels. Its impressive how different each of them sounds, and also annoying, lol.
Sony Pulse 3D; closed back, so its sound by default is totally different. That being said, it has a smooth response, but with what seems to be a boosted low end either by design or due to being closed back. The "soundstage" for these is small compared to the others, but that doesn't really matter too much as the sound is really clean. The biggest negative with these is that being closed back has them pick up every little head movement / cord movement.
Sennheiser HD599; have had these for many years now, compared to the other two it has a pronounced bump in the mids.
Sundara; still really new to my ears, but being open back they sound much different than the Pulse 3D's (both planar). Not nearly as strong of a bass sound as the Pulse, but more detail / depth to the lows than with the 599's, overall it sounds flat but with solid low end. Reminds me a bit of a pair of Sony MDR-somethings I had like 20yrs ago.