It seems that if you own a pair of the cheaper HD555 Sennheiser headphones you can upgrade them to the more expensive HD595 headphones for free, so long as you own a screwdriver!
http://mikebeauchamp.com/misc/sennheiser-hd-555-to-hd-595-mod/
Awsome find TL, the missus got a pair of HD555, so i gotta try this out!