It seems that the more you take the baffle and cup out of the way, the more neutral they sound. Given how fast Sennheiser introduced the 2002 model (with a modified cup) after the 2000, it's probably not a bad guess to make that the cup design on the 2000 wasn't even close to optimal, or even decent.
Curiously, bass extension didn't suffer when the cup was taken off. Doesn't start dipping until about 35 Hz. Treble isn't as harsh as before, but I attached a foam disc directly to the back of the driver - might have something to do with it. Soundstage is a bit more open, no surprise there.