Kiats
Headphoneus Supremus
Since you own almost all flagships, it makes sense to own HE-6, too. Not sure about EF-6, I demoed and did not think to own it as it takes up so much real estate.
I am thinking about downgrading to the HE-560 so that I wont be constantly asking this question to myself "can it drive the HE-6?". It can be frustrating when I dont have the dough nor space to buy more amps. I guess it wont apply to you since you already have the he500.
Heheh! The HE-500 was an opportunistic purchase. Totally unplanned. Bought it off a nice young man. But, yes, the HE-6 is the last frontier. And, yes, that question that bedevils you concerns me too. Hence, the hesitation. We'll see...