At least with my setup, HD6XX easily performs better. Although Elegia is closed, I was pretty underwhelmed given it's price.
Don't get me wrong, HD600 performs really better on some aspects, especially in terms of soundstage, airyness, low and mid midrange timbre (which is really spot on on the HD600), but the Elegia sounds less boring overall to my ears for rock, folk, jazz and most vocal tracks (mostly female voices), but it's my very personal opinion. HD600 is a better performer in some aspects, but it's an open-back pair... In terms of price, HD600 is the better bang for your buck by miles (you can buy 2 pairs of HD600 for the price of one Elegia, it's a no contest there)... But given that there's not plenty of choice in the closed-back category, I think Elegia deserve its place between the best pairs under 1000$. But again, it's very personal...
I also did some comparisons between Elegia and my AKG K550 Mkii. I prefer the Elegia, but again, Elegia doesn't sound 5 or 6 times better than the K550...
Also, given the fact that Elegia are pretty mid-centric, they will definitely not please anyone there.