Well, there goes the resell value of the 600 and 650s!
https://www.massdrop.com/buy/massdrop-sennheiser-hd6xx?mode=guest_open
https://www.youtube.com/watch?v=pUKbI8p2bRk
https://www.massdrop.com/buy/massdrop-sennheiser-hd6xx?mode=guest_open
https://www.youtube.com/watch?v=pUKbI8p2bRk