I did that upgrade and compared them side by side. Overall, Arya Stealth is tighter and faster sounding headphone with a bit smaller stage but better separation, detail and all that. Considering Arya Stealth's price drop i strongly recommend the upgrade however XS and Arya Stealth different headphones. XS has more spacious sound and light clamping force, Arya Stealth is more energetic and bold. More physical, less gentle. More immediate sound.
XS is fatter and looser in the lower frequencies and more gentle in the upper frequencies. Arya Stealth tighter, faster, bolder in lower frequencies and sharper, energetic in higher frequencies. XS has more upper treble and air. Arya Stealth is more precise, less echo and upper treble noise.