Try it. I have a feeling you'll find that the HD800 is not the mighty T-Rex as and the HE-500 is not the puny raptor, more so, the HD800 is the T-Rex and the HE-500 is the Giganotosaurus, so to speak. Extremely comparable. Countless hours of listening and different amplification show, at least for me, that the reason the HD800 is supposedly a sonic league above the HE-500 is due to three things. Again, this is opinionated, and I would be saying the same thing for any other high-end comparison.
1. There's a slight difference. But, it's blown way out proportion. Also known as hyperbole.
2. The HD800 is twice the price of the HE-500, and the minute you lay down the cash for an HD800, you have a bias and a little voice that goes on inside your head that says: "Since the HD800 is twice the price of the HE-500, it must have double the sonic capabilities, therefore it does!" Which, in my opinion, is not true to life. Same for the HE-6.
3. Psychology. Our mind is capable of seeing and feeling many things that really aren't there. And I believe the "sonic league differences" you hear between the two are really just mind tricks.
Oh, and just to add. I try to find the best headphones that fit me, I don't care about finding the Summit end of audio or anything like that. I was loaned the HD800, and the HE-6 + Stingray from a friend who's more Into speakers, but likes headphones as well. And I traded to get the HE-500 a while ago, because I compared all three and the HE-500 came out on top. No money laid down, no pre-bias, IMHO.