Did your HE-500s come with the silver cable?
I just purchased my HE-500s this past Tuesday... they are burning in with about 96 hours so far. This is my 2nd HE-500s... the other ones I had shortly after they came out. Without being able to directly A-B them, I would have to say they have been improved some. I think the silver cables helped them also.
They are really opening up now, and I helped them a little by taking the cloth off the outside metal grills. It was like removing a veil... which actually it is. I also have gone back to the GE tubes in my Lyr from Schiit. And I use the Bifrost with an Oppo 83SE player. I have been switching in and out with several other tubes, including Amperex Orange label, but with the leather pads, the GE's really shine.
I tried the velour pads, and they were a little muffled... like a couple of veils. That's strange because I liked the velour pads with the earlier HE-500s and also with the HE-400s.
I will say now... hands down... these HE-500s are the best phones I've ever owned... and I've had the HE-5Le, HE-400, Senn 600, 650, 800, AKG 702, Beyer 880/600ohm, Grado 1000, and others. These are keepers!
I am interested in getting an upgraded cable. You seem to like the Norn Series 2. But, what are the other pieces in your chain?
Also, which Norn series 2 did you get? And how much is it for a 10 foot cable?