I've just received one of the Noblechairs Icon series and I much prefer it to the Markus, which I tried a while back and wasn't a patch on the old Klappe (the Icon is the first I've tried since the Kappe that I really liked).
I can't really compare it to the Corsair chair as I haven't tried that, it would be hard for it to beat the Icon based on the number of chairs I've ended up trying in the last year or so.
A few things to bear in mind with the Markus vs the Noblechairs Icon.
The Markus has a lower weight limit (110kg vs 180kg), it has less adjustability, and personally I'm not to hot on bracket that holds it's back in (it seemed flimsy to me), I'm not sure if it's a Markus my brother has got at the moment with a dodgy back.
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I've just been talking to my brother and his description of the markus was "awful and falling apart", it turns out he has been feeling the screws that hold part of the armrest together through the thin padding on the arms.
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