TonyL: Im very interested to read that you are waiting to take delivery of a Nagaoka MP500. Had I stumbled on this thread a bit earlier, I would have posted sooner to maybe give you a little warning. Nothing drastic, but my experience with an MP500 was frustratingly mixed.
The back story, briefly, is that after having run a Notts Analogue Ace Spacedeck with a Hadcock arm for years, I wanted to try something different. I therefore bought a Garrard 401 and a SME M2-9R to go with it. Imagine my annoyance to find that neither of my previous go-to MM cartridges (Music Maker III and Decca Gold) could begin to track a record satisfactorily on the new arm. They were as nervous as kittens with anything, and given a record of piano music they were really unhappy, with the Music Maker very prone to skipping chunks of the recording at a time.
The solution was to buy a second-hand MP500. Well, this is a cartridge that oozes quality. I was very impressed. Set it down on the record and the first thing you can see is it tracks anything - really anything. I think if you turned your turntable on its side the cartridge would keep tracking! The problem - for me - was the sound. Yes, it was fantastically refined, smooth and precise. I would describe it as a very "elegant" sound. The attributes of weight, space etc that you mentioned in your earlier post are all there.
BUT ... it had what to me was a decidedly dull top end. It was very rolled-off in the upper frequencies, which robbed it of any sparkle to go with the gorgeous velvety-ness of its other registers. Now this may have been a problem with the arm matching, or it may have been a cable capacitance issue. But whatever it was, I couldn't get past it. I kept it for a long time, loving 85% of what it did, and really willing myself to accept the last 15% as-is. But ultimately it was just a bit too snoozy for my taste, so I sold it on.
I still feel a bit sad that we didn't get along a bit better, even now. It is a real aristocrat of a cartridge, but I will be very interested to hear how you get along with yours.
ML