Circumstantially speaking, I would send it back to HeadRoom for a replacement.
Since your post does not include that, yes, I would probably buy another HD650, since I do not have/nor have I heard another comparable headphone. It depends on how the HD650 acts with the WooAudio6 I'll eventually have, though; if I find the HD650 to be a bit too dark with the WooAudio6, I would maybe get an HD600 to replace it if the HD650 were destroyed and out of any kind of warranty.
edit: Some people don't seem to understand what Lucky was getting at (or are joking). Or, perhaps, I don't, if he is taking into consideration warranty and such.
edit 2: ah, looks like people get it, looking at the votes.
Of course I wouldnt, why would I buy a new pair of the same headphones if they break that easy. I wouldnt care how it sounds, I would go for another pair which doesnt break as easy.
You have I think missed the point. There was no talk regarding the ease of fault. The question should be read as "do you like the sound of your headphones so much that you would buy another pair of the same if they died?"