Just a heads up, I'm happy to announce that the extra large (XL) version of the Casebudi case fits the X1 perfectly:
The width and depth match the X1 perfectly. There's perhaps an excess of about 1cm vertically, but it's nothing major and I doubt there's a case that fits it more precisely.
There's no padding on the interior, but I suppose that's standard as far as generic headphone cases go.
I realize that the box the X1 comes in is quite strong and protective, but it's humongous and impractical for daily use for me. Plus, the box isn't really replaceable and I don't want to subject it to unnecessary wear and tear.
This one does.