Hi .. here is a belated 2007 comment on the Sennheiser PX 200. It arrives now as I just received a non-returnable pair for Xmas to use with my iPod Touch.
I have never used headphones much.. but .. your review seems to me to be dead on. I know that there are better phones (e.g. the Grado SR 60/80 at al). However, as I "check the sliders" on the iPod EQ -- they seem to fill the mid-range hole that you have reported.
On close, they are pretty good -- but their closed design just cuts the kind of live ambience that you can get with a non-closed design like the Grado's.
The bass PUNCHES too -- just listen to The Eagles - Hotel California.