Well this is a fine how-do-you-do...
So far I've compared the ESP-950 to the following:
Hifiman HE-400i
Oppo PM-3
Audeze LCD-2 (pre-fazor)
Monoprice M1060
And in each case I found the ESP-950 superior once EQ'ed, especially when run off the Stax SRM-1/Mk-2. I would have liked to have spent more time with the Monoprice 1060, but the manufacture quality was apalling... depending on what Monoprice fixes for the second run, I may revisit them as the bang-for-the-buck is insane.
But I wanted to try a set of better closed headphones, looking for a bit more impact and bass.
Enter the original Fostex TH-X00 (Mahogany). I picked up a set second-hand on eBay. Damned if it doesn't hit a lot of the sweet spots. Much better than I was expecting.
Treble was harsh as a mofo and way too high until I EQ'ed it down (makes me think that had I ever auditioned Sennheiser 800/800s I would have run from the room screaming). The X00 is nowhere near as detailed or analytical as the ESP-950, but I'll be darned if it isn't more "fun", for lack of a better word. Definitely not a flat headphone, but whatever they're doing makes the music seem more alive, especially on music with a lot more dynamics (rock, metal, dance). They've got my head bouncing more than the ESP-950. The soundstage isn't as large as the ESP-950; the music is more immediate and "in your face".
On classical and acoustic material though, I still prefer the ESP-950, genres where the detail shines and soundstage plays more of a factor. But for sheer sound presence on modern music, I greatly prefer the Fostex.
Comparing the vastly different sound signatures and presentation makes me wonder if it is truly possible to have a single set of headphones that excels in all areas. Right now, I'm listening to the Fostex about 80% of the time, but there's that 20% of material that has me reaching for the ESP-950.
It really does appear that "there can't be only one"... which I hate. There's nothing more annoying than having to choose different cans for different recordings/genres. If I had never heard the ESP-950, I would have been perfectly fine with only the Fostex... and vice versa. Not to mention the cans above that led me to these two. Oh, the journey...