I have that same case, but I've now found a better case for the WP900 and have since relegated that one for my MSR7B. It's this:These are great portable cans. I'm using them with my Dragonfly Cobalt and the sound quality is excellent. The earpads do warmup your ears after long listening sessions. Everything else about them is fine. They are lightweight, bass is weighty and textured. Vocals are clear and slightly forward. Treble has good clarity and presence. All are nice attributes and what you want in a set of quality portable headphones.
I'm toting them around in a GoCase, I had sitting around that I've seen another head-fier using and it works out nicely. I just wish I didn't have to connect/disconnect the cables every time I wanted to store them.
It has the advantage of keeping the cups apart and is slightly larger on the inside. The cable wallet thingy is also a bit larger. Details here.