I was bewildered why my MP-200 was sounding so thin and shrill, but as an experiment I put the 200 needle on my mp-150 cartridge and immediately the bass and dynamics were back. Not sure what's going on there, but my suspicion is that I bought the whole mp-200 with headshell and that nagaoka headshell was lighter than the standard Technics (so maybe Nags like heavier headshells?), I had to adjust the counter weight to compensate a tracking force of 1.8g. You gotta love Analog....
BTW, this whole conversation has got me researching affordable MC carts and probably the next one I would try is the Denon DL-301 mkii. I haven't heard one bad review of it and a couple vinyl rips sounded really good. Might also keep Denon in mind...