I got a pair of HE-500's two weeks ago and after a few days installed some HM5 sheepskin angled pads. First I tried the original velours, which were quite uncomfortable (but sounded good). Then tried the Focus pads (or Focus-A's, not sure which these are) and got more comfort. I was maybe hearing something off in the highs, very much not sure though... Then I realised the mounting rings come straight off from the pleathers (didn't even try those, I'm feeling discomfort just looking at those shallow things), nice!
It was a bit of a hassle to get the oval and tight HM5 pads over the rings, but I managed eventually. THIS is what I was looking for sound-wise - punchy, deep and present bass without audible anomalies in the other regions. Having LCD-2.1, HD800 (EQ'd) and HD600 to compare to these are some very nice sounding, surprisingly neutral headphones. A slightly sparklier, more fun HD600 with better bass presence, speed and punch. Better soundstage too, I'd say.
That stock silver cable is a horrible joke for an hp of this quality, microphonic & plasticky as hell. What were they thinking? Yeah, it's light, but please put some effort into it.