Mm...I will bequeath my HE1 to my furkid....a poodle, Chealsea.
My Erlkonig silver cable is terminated 4.4 mm. So I had to buy a 2.5 mm silver cable Made in Japan. No available 4.4 to 2.5 mm adaptor. No songs yet except for a couple of preloaded songs. From what I can hear, the SP 2000 cu just puts to shame my Ak380 cu. Night and day difference. Gloriously open, transparent, musical sound. Soundstage is huge.
I auditioned in HK the SP 1000 cu and SS and the SP 1000M in 2017 and 2018. From memory and if I had to make a spot judgment, the difference in SQ is not huge (SP1K cu vs. SP2Kcu).....maybe the later is more refined sounding.
Need much more time to listen and settle down.