I bought the 3-pack of Koss earpads once. They are a bit thinner, and larger in diameter than the stock pads. Since my stock pads were not damage or worn, I decided to mess around with the Koss pads instead. I believe I did a quarter/nickle mod to one, a penny/dime mod to the other, and I can't quite remember what I did to the 3rd. Overall though, I still couldn't break away from the sound of the stock pads, but I could assume there would be some listeners that would enjoy the benefit of modding the Koss pads. And for only about a dollar a pop, I'd say that's plenty worth to experiment with new sound.
I've compared too many headphones to the PX100-II and usually favored the PX100-II each time (as the review says). But the first time where I started questioning how good the PX100-II really was was when I first listened to the MA900. They were the first headphone that I actually preferred to the PX100-II since first purchase. Since that was basically the only headphone I preferred, I wanted to hear it against my long previous favoirte, the HE-500. Fast forward a bit and I acquired my 2nd pair of HE-500, and 2nd pair of MA900, side-by-side. Pretty sure I posted the results in another thread, but I actually liked the MA900 more. I had a notepad up and documented each song compared, what I did and didn't like between headphones conveying the song, and the overall score. MA900 was preferred on most of the music.
I've got the Annie now, and I haven't heard a headphone quite like this one in a long, long time.