The GSP models aren't actually Sennheiser, I don't think. It's a collaboration with EPOS Audio.
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Well it still has Sennheiser's name on it, but that's a good point. Gonna avoid anything with EPOS like a plague from now on.
Maybe EPOS' non-gaming hardware fares better, I have no idea. But these headsets certainly aren't indicative of Sennheiser's own production.
The closest thing is probably the G4ME ZERO, which is based on HD 380, which in turn has another headset version in PC 350. Similarly, there's an open-back headset based on some HD 5xx model. These are okay and should have replaceable parts. They're not perfect though, and there have been well documented quality issues too.
However, Sennheiser also has a professional product line with models such as the current HD 26 or HD 300 Pro that have HMD counterparts. These should be rugged and serviceable, but potentially not the most convenient for regular users. I'm a huge fan of the older HD 25 and HD 250 though.