@yeboyi In regard to your soundstage or congestion assessment, I would note that the HE1000se is more sensitive than the Arya Stealth such that when plugging in their input sensitivities and impedances into
https://headphones.com/pages/headphones-power-calculator, the HE1000se would require less power to attain the same loudness level. For the same input signal out of the same amp, assuming both headphones are being driven with singled-ended or balanced cables for a fair comparison (the latter would sound louder), the HE1000se would be playing around 1.5 dB louder. If you
did play around with the volume knob while A/Bing, and the Arya Stealth remained small and crowded even when played louder than the HE1000se,
then I may remain interested in experiencing that model someday. To confirm, both headphones have a similar amount of space around the ears within the cups, right? Is the fit of the pad fairly similar for both?
Otherwise, as far as I've found, perceived "soundstage" tends to increase with loudness. Now, comparing
https://crinacle.com/graphs/headphones/hifiman-arya-stealth/ and
https://crinacle.com/graphs/headphones/hifiman-he1000se/, the latter does seem to have a slightly deeper 2 kHz dip which could contribute to a slightly greater sense of distance. The remaining differences in the treble can of course have varying subjective effects, especially the positioning of certain peaks specific to your ears. I would recommend playing with PEQ peaking filters of a Q factor of 2 centered around 1.7 kHz and 6.4 kHz and comparing the subjective result of increasing or decreasing either, or if you are patient, using those frequency responses to produce variable-band graphic EQs that would theoretically transform one into the other.
As for imaging, after volume matching the playback between the headphones, how does the imaging of the pencil at the start of
differ between the headphones?