Best Headphones under $500?

I've come into some extra money and I want to buy a new pair of headphones. I am currently using the Sennheiser HD 558 with the Schiit Audio Magni and Modi. I've already looked at offerings from Sennheiser and Beyerdynamic, so I wanna get some different opinions on this. I also want something with great soundstage and instrument separation. I mostly listen to metal and EDM as well as spend a lot of time playing video games.

Requirements:

- Open back

- Circumaural

- ≤ 600 Ohms 

I would look at the HE-500, if it were me. You might be able to pick up a used pair somewhere. The HD600 is another option which has great instrument separation. Look for some reviews of and see what it is that you are actually wanting for the sound signature. Just so you know though, if you want something that will be good for EDM, then you should not be looking at open backed headphones. You need to realize that a jack of all trades is a master of none. Metal and EDM? Not likely. They need very different things. Metal needs spacious, open sound (more so with the more technical genres like techdeath than things like power metal), fast sound, disciplined bass, and tons of detail. EDM needs impactful, clean bass that slams hard but doesn't get in the way of the rest of the music. So when you are looking at headphones, keep things like that in mind. For example, the HD600 has great separation, but is too laid back for most metal. Meanwhile something like the DT880 has the detail, speed, and separation for metal, but doesn't have the bass response for EDM. Something like the HE500 or the Mad Dogs could be a promising compromise which can do both fairly well (the Alpha Dogs are a great option if you can increase your budget a little). However, you might find that you would be more satisfied if you got two different sets of cans. One for metal, and another for EDM. That is what I do, personally. I like the HP100 for EDM (has great bass impact), but prefer the Q701 for stuff like metal and rock.