High Performance Moving Iron Cartridge Candidates?

Some questions about Soundsmith. As I understand it earlier cartridge designs were built upon the B&O architecture. Is there some point the designs evolved past them? Are any of the current cartridges still based on them? 
 

One thought comes to mind. Soundsmith won't be around forever, or will at least transition at some point. I don't think we can bank on their rebuild costs model staying the same whenever things do change. Koetsu is a recent reminder of this. 
 

Grado is a cartridge I have never been fond of. Do the Nagoaka have a bit more sparkle and presence than them? 

No doubt Soundsmith and other audio companys wont be around, as they are today, down the road. 

I have come across a couple other services that rebuild carts, so hopefully that is an option if needed.

I think Soundsmith's site may have some history on the B&O builds.

I think PL was influenced to get into MI cartridge development and manufacture by his prior experience with top of the line B&O cartridges, like the MMC1 and the MMC20CL.  So he first developed the SMMC line of SoundSmith cartridges, which he still sells.  The SMMC cartridges are virtually copies of the B&O MMC series. And SS specialized in the repair of B&O cartridges early on. In my opinion, the MMC1 is one of the finest sounding cartridges ever made, so I very much understand why PL chose that path.  As to whether the SMMC cartridges are structurally related to the Voice and its successors, which get ever more costly as you move up the line, is something only PL can say.  But you could do worse than to go in that direction. As to longevity, none of us will be around forever, so buy what you like and forgeddaboudit.  If the cartridges you leave behind are a significant fraction of your estate, you ought not to be dabbling in this area.

Also only in my opinion, HOMC cartridges are the least good sounding of all types of cartridges that I have heard, and I have owned some purportedly very good ones. I’d much sooner own a Grace Ruby, even with the OEM elliptical cantilever, although the SS OCL stylus does take it up a few notches.

Taken a look at Audio Technica ART9xi - not much iron to move, but a massive magnet structure, and SLC stylus profile.

Simply wonderful sounding, and very high output:

Apparently replaced by the ART20:

https://www.audio-technica.com/en-us/cartridges/line-series/art-series/at-art20

My understanding is that Peter has someone who works with him on the high end cartridges, presumably so that one day they can continue the work. I have not asked Peter that directly (an excess of delicacy on my part), but I have heard that from a dealer. With cartridges like the strain gauge and the Hyperion (with its cactus spine) one is dependent on SS for future service. Those with more conventional builds could be serviced by the usual suspects.

@neonknight I hear you about the Grados. I have a Statement 3 that sits unused. I can't say there's anything wrong with it, but it doesn't excite me. The MP-500 I discovered when I was concerned that the Deccas would no longer be serviced with John Wright's retirement, and it comes close to the Decca sound and liveliness. Initially I didn't hit it off with the Sussurro, but with some very careful attention to VTA it suddenly came to life and impressed me enough that I moved up to the Hyperion, which is better still. I rather hate to say it, but it is better and more engaging than the the Decca. I never thought I'd say that. If you can stretch to one of the Soundsmiths I think they can outperform the MP-500, but as I say I haven't heard one of the high ouput SS cartridges. PL himself says he only makes low output versions because the market demands them to use with expensive MC phono stages, and he implies that if it weren't for that he'd stick with the high outputs.