Analog Gurus - What cartridge after Grado Ref 1???

Try a nice used Lyra helikon.VandenHul Frog also.

I started with a Grado Prestige Gold, then jumped to a Koetsu Black, tried a Reference Sonata and a Benz Ruby when the Black required a retip but eventually tried a Statement Statement and haven't looked back. No hum from any of the Grados I have tried and I find that Grados maintain the PRaT and warmth of the Koetsus without the sometimes glassy etchings of MCs.

Your setup is similar to my own: Gorbe to full Orbe these days with a SME V. I am constantly charmed my the music I hear. The higher you go in the line, the more detail retrieved, particularly among the Statement series. These approximate a MC sound without what some consider drawbacks. After having listened to various multi-thousand dollar carts in various astounding setups, I don't think I would ever buy anything other than a Grado or Koetsu, given my preferences.

You have what I call the "Grado Problem." That company makes lovely, musical cartridges that make it very difficult to find something significantly netter at a sane price point. I didn't even try. I love my Reference Sonata/PH-1 combo.

I would say if you're happy with your music, stop. Your exit point has been reached.

I have a Grado Reference Sonata 1 (5.0mv output) and a Grado Statement Sonata 1 (0.5mv output). The Statement is by far the superior cartridge in my opinion. Clear and nuanced. Almost as much of an improvement over the Reference as the Reference was from my Grado Signature 8, which blew away my Prestige Gold. No hum problem at all, the motor in my TT is shielded, Grado cartridges are not.
The only problem worth mentioning regarding the Statement is it's low output. You're going to need a preamp with a lot of gain (close to 60db) and with that will come hiss.
A friend has an Ortofon MC, don't know what model but it's output is even lower, around 0.25mv. His solution to the high gain hiss problem was to run it through a DBX processor. The sound is pleasant, but I prefer mine. Otherwise, our systems are very similar.
I listen to the Statement but keep the Reference on a spare headshell as backup for quick swaps, they both weigh the same. I use the backup for 45's and to evaluate used vinyl.