I purchased a pair of these angled velour pads to try with my HD600:
http://www.amazon.com/gp/product/B00ZGFVEUE?psc=1&redirect=true&ref_=oh_aui_detailpage_o01_s00I'm very pleased and am really enjoying them. They're slightly deeper than the stock Sennheiser pads, so my ears no longer touch the back of the headphone - plush and comfortable. I've always found the the 6xx Senn's headstage to be sufficiently wide but lacking in depth; the angled pads are definitely an improvement, pushing the stage forward a bit, resulting in more dimensional imaging. Mounting the pads required tearing off the two-piece mounting rings from the old stock pads and adhering/sealing them to the Brainwavs pads, not a big deal. I used "krazy glue" and would have to imagine most strong glues would work fine. The pads are thicker than stock however, so a bit of additional bending of the headband may be required for an ideal fit.
Pads installed on the HD600:
Mounting rings attached to the Brainwavs pads (the
on the rings is dried glue residue...whoops):
A look at the angling of the pads: