Magick Man, can you do a quick comparison on ESP 950 & HiFiMAN HE-6 & Denon AH-D7000, please?
Okay. The HE-6s are brighter, more "edgy", have neutral mids, smooth yet powerful bass, and their imaging is top notch. Downsides, they may be too bright for some people, and they really need a gutsy amp to get 100% out of them. A lot of owners run them directly off the speaker taps on the back of a two channel integrated amp or receiver, and that really is the most cost effective way of driving them. Unless you're like me and you run them off a $4000 Cary tube amp. Hey, don't judge me, it's an awesome piece of gear.
The D7000s are more bassy, have somewhat recessed mids, and a sweet and sparkly treble. They're more colored than the other two, but are awesome with pop and bass-centered music (Dubstep, Hip-hop, etc.). For a semi-closed headphone they have very good imaging and are quite comfortable. Also, they're very easy to drive and sound exceptional out of practically anything, including small MP3 players. The one major downside is that Denon isn't making them anymore, if you buy a set there's no telling if you'll get proper warranty service. Also, some gripe that they're a little boomy, but I don't think so.
The ESP/950s are mostly neutral with slightly colored mids. Their bass is dead-on accurate, and they have very detailed highs with a little sparkle at the top end (8-10kHz). They're great with just about anything, except perhaps metal. They have the best imaging in their price range and aren't equaled until you get over $1000, where they're tied with the HE-6s and surpassed by the HD800s (at twice the price). Also, there's the lifetime warranty that covers everything. They also come with their own dedicated amp, the E/90, which is said to be pretty solid. I don't own one, my 950s were used and didn't come with it, so I run them off my STAX SRM-717. Downsides, they feel cheap and "plasticky" compared to the other two. Also, if you do decide to get a better amp you're going to need an extension with a STAX plug on one end, and high end electrostat amps are very pricey ($2500+).
What would I do? Get the ESP/950s ($650), a set of Denon D2000s ($250), and the best used Grados I can find for ~$400. That's about the price of the HE-6s and I'd have more variety.