Well If my KSC75 died on me, I would replace them (and they actually have, and I did - LOL)
There are a couple of HD555 on the for sale forum for $50, and you can't go wrong for that price. They would be an upgrade for gaming.
I think Koss has a lifetime warranty on the KSC75, so if you pay $5 shipping or something Koss will replace them.
So I would go that route ^, and get some 555's if it were me....