It's a bit early for me to dissect them fully but they are a faster sounding headphone (typical of this tech or electrostats), they are thinner sounding overall, not as "rich" compared to the PS-1000s but again, this is typical of the tech. The highs, as others have mentioned, are very very dependent on amplification. They can be strident, with an odd peak somewhere up there, but with better amplification, things are smoothed out. The bass is very nice and fast and again, with more power comes better bass. The bass is not in the same league as the PS-1000's where the bass is very much a forte of those headphones. At the same time, the bass is tight, deep enough for most music and there is no apparent bump anywhere in the lows or mids. As others have mentioned, compared to electrostats, they have a bottom end

Some may feel the HE5s are as good or better than the PS-1000's. I can foresee this from those who really love the electrostatic sound. I think the HE5s are better balanced than any electrostatic headphone (and I admit to being pretty wet behind the ears when it comes to orthos, with a bit of experience with Beagle's Yamahas).
Again, for $600, one gets a very fast, nicely balanced, warm electrostatically fast headphone without the sick pricetag of both the phones or the amp
