I just picked a Sennheiser HD558 to complement my older HD555 I just cleaned up (replaced the cushions, cleaned the drivers, did the HD595 removal of foam mod). I've had that HD555 for over 8 years now, and I would highly recommend those or the newer HD558s easily.
I'm a huge fan of Sennheisers for open-ear headphones, but for environments where I need closed, I've got a Shure SRH440 that is pretty awesome. For travel, I've got the Sennheiser PX 200-II, which replaced an older pair of AKGs that didn't feel so good over the ear. The folding AKGs did have better sound though.