I just made a mod to my M50s which is very simple: New angled pads.
I took delivery of the NVX XPT100 due to a recent sale ($100 for this Fischer FA-003 clone, plus the NXT clone of the in-ear VSonic GR06).
Inside of the NXT box were an extra pair of these:
They look like a pleather oval version of the Alpha Dog pads by Mr. Speakers. The design is a little weird, though, as they are really two "right" pairs of pads. Basically this means that the seams will be on opposite sides (bottom left and top right) when installed.
I look at the size and think, if I take out the plastic mounting bracket from them, these might fit the M50s.
Well, it is nearly a perfect fit. Now I have what might be called ATH-M50 Alpha headphones.
So, what changes? Comfort, for one. The M50s are now super comfortable. The angled pads mean my ears no longer touch the foam inside of the pad. In fact, you can even adjust the toe in of the fit to change the pressure between the front and back of the pad very easily -- really useful for longer listening sessions. Next, they have better imaging. There might be a bass bump, as well, but I'm not going to swap back and forth to check (don't want to damage the pads).
On the downside, the pads do have a little play in them when mounted, which means positioning becomes a bit more of an issue when you first put them on. I think of that as a plus, though, because it helps with long-term comfort.
All in all, a big win.