My HE-500's arrived today along with a Mytek 192 DSD DAC and some Oyaide firewire and USB cables. The Mytek is one of a handful of DACs that can accept a firewire connection. Source is a 2010 Mac Mini with Audirvana Plus.
Even with both the HE-500's and Mytek, cold out of the box, the sound is quite luscious and delicious. Been playing a bunch of songs and albums ranging from 16/44.1, 24/96 and 24/192, all in AIFF format.
Oddly enough, my HE-500's came with the silver cables instead of the newer black Canare. All's good though since I was going to buy the silver cables anyways, now I'll just have to buy the black Canare cables.