...my experience, the HD600 + EarMax Pro combo was awful. The bass was huge and bloated, they had a very non-intimate, distant sound and the entire range had this ugly electronic glare to it. After a week and a half of straight burn in, things did not change and I simply could not salvage the combo in my mind.
It was supposed to be a great match and I don't doubt that some like the sound or that perhaps I got some bad HD600's or something, but GAWD was it awful. Every time I'd put them on, I'd immediately yearn to take them back off again.
All the details hidden in the background were there, but they were just plopped down and presented, rather than constructing some mystique and giving them to you in a 3D soundspace. They were all brought right up front with everything else, so to me, the overall sound lacked a real third-dimensionality and texture, whereas with other cans (W100's, Etys), the sound was extremely deep and sound sources were placed not only left-to-right, but also front-to-back.
However, I went to my local Headroom show and heard the HD600's on a Blockhead and I must say it is by far my favorite sub-$5000 headphone setup. The most solid, definite, lively soundstaging I've ever heard, by far, clarity and distinction of musical tones, a natural perspective on the music (not a hyper-real, ultra-close one, but a natural one, like it should be), skull-rattling power, etc. It was great and I'm still "high" off of it.
With this in mind and my bad EMP + HD600 experience in mind, perhaps, possibly, maybe, the Corda or an RA-1 would be better, being solid state.
Hope this helps.
- Matt