Is there usually a dramatic difference between $5k and $10k cartridges ?

OP seems like a lot of $$$ to get a 2nd cartridge (mono) and another tonearm and possibly a tonearm cable for how many mono LPs? 🤔

If most of your listening is with stereo LPs then my choice would be to upgrade the stereo cartridge. But it's your system and choice. Do keep us updated. Enjoy your journey either way it will be fun.

Yes, Raul, I don't expect a simple answer, I am interested in discussion.

Perhaps it would be better in most cases to first seriously upgrade tonearm before even thinking about $10k plus cartridges. Not to mention table and phono stage.

mulveling, that's what I assumed. No guarantee, let alone "dramatic difference".

For some of us $5k difference is nothing but for many it is a lot.

Personally, I would not play this MC game and would seek out best vintage MM cartridges. But that's me.

Thank you @dwette that is the answer I was looking for. No speculation on my setup but confirming that the different/better experience with quality mono cart with my type of music. I will buy the Miyajima, or other good mono cart, then try it on my existing system. If that works, then add second quality tonearm. Expensive but fun hobby...It is great to find some that actually have made greater investments and sharing their experience. 

@luis223344 What’s nice about my setup is I have the exact mono counterpart to my stereo cartridge (Lyra Atlas: SL + Mono), both on identical tonearms on the same turntable. Both also run through the same phono-stage.

I’ve been able to really see what a true mono cartridge brings to the table, i.e. comparing Atlas SL with mono button engaged vs the Atlas Mono. Some mono records almost sound stereo with the depth of soundstage the mono cartridge adds, and they play so quiet since the mono cartridge ignores the noise of the vertical grooves.

I think it’s worth it if you have a collection of mono records you play often enough.