Good idea. Friend of mine has a WES and Omega System. I can go and try :)
I am both using HE500 and HE6 from a speaker amp. (Primaluna Prologue Two, 40W per channel) All rig is modded and upgraded. (Tubes, cables, feet, amp etc) So I dont think there is a problem with my rig.
I am trying both with leather pads and it is not that much difference. Bigger than %10 but not apples and oranges.
I'm sorry. But IMHO the HE-6 is far better in every way than the HE-500. However, you must amp it correct. Like captoch is doing with his HE-500s. If you put the HE-6 on a speaker amp you'll see. It's an headphone experience you must have. I have not heard many STAX headphones except at a few meet. The HE-6s when amp properly rivals some Stax headphones. Please try it out then come back with your impressions.