I find that the HD700 is amp sensitive. Love them with my Lyr and Amperex Orange Globe tubes. Really smooths out the highs. Tried some other recommended tubes and I couldn't last more than two minutes with them. Highs were just too much. Tried the Schiit Magni just for kicks and sold it after two weeks.
Just picked up a pair of HiFiMAN HE500's two weeks ago. The HD700 really holds its own against them. If I had to pick between the two, I think it would be the HD700. They really compliment each other. Greater detail, tighter, but less bass, a little more exciting, awesome for vocals and jazzy music and of course, much more comfortable. The HE500 are silky smooth across the range, especially the mids and are incredible for club type music. I think the HE500 still need a little more break in, they have about 150 hours, but for now, the Senns have the edge for me. YMMV.
On the other hand, If I was asked for a recommendation, it would be the HE500. They would sound better across more sources/amps.
For the first time, I have two pairs of headphones that I really, really love.
Edited by MickeyVee - 3/8/13 at 5:11pm