Amethyst versus Nagaoka MP-150/MP-200

Does anyone have any experience with these two carts, by any chance?  I have the Amethyst and I've used it for about 40 to 50 hours now. I think it's a beautiful cartridge, and I'm a fan of Sumiko in general, but it doesn't hit the spot like some of the other carts I've used.  So I think I'm going to sell it and buy something else.  I've had my eye on the MP-150 for a while.  Would be curious to hear folks' thoughts on this cart, especially from anyone who has heard the Amethyst, too.  (Also, if anyone has thoughts on what a good selling price for the Amethyst would be, please let me know.)  Cheers.