For what it's worth I have Sennheiser HD580 headphones I bought almost 30 years ago which are still fine. I just replace the pads every few years and have replaced the headband foam once. If you want a buy once keep for life headphones then if current HD6xx products are built to the same quality then you won't go wrong buying them. A bit above your budget but there are always offers on them and if you really want a long term product then you might be better spending a little more for them