Cartridge upgrade for Goldring GR1.2 turntable

I have a friend who bought a Goldring GR1.2 turntable on closeout from Audio Advisor (about $216) on my recommendation six years ago. The GR1.2 is pretty much a Rega RB2 clone or copy, and from what I've been able to find out, came with a Rega RB250 tonearm and Goldring Elektra cartridge.

He recently got a Marantz PM8004 integrated amp, which, if you're not familiar with it, is pretty fabulous at its $999 asking price and includes a MM-only phono section of a bespoke design using discrete components. He's really enjoying the improvements, but it's kicking off an upgrade bug to bring the rest of his system up to the same level.

So he's looking to upgrade his speakers from Klipsch Heresys and wants to get a better cartridge as well.

I don't think he's going to consider carts above $500, nor LOMC carts because he'd need an outboard phono stage or stepup device. Based on the RB250's 12g effective mass and 4-11g range of cartridge weights, my short list of upgrades are the Audio Technica AT150MLX, Grado Reference Platinum, Grado Prestige Gold, Nagoaka MP-150 or MP-200, the Goldring G1012GX, or the Ortofon 2M Blue or Bronze.

Are there any good candidates I'm missing or is there a standout among the ones I've listed?

I have owned the Ortofon 2M Bronze and current listen to the 2M Blue. Both are very nice but for the price, I would go with the Blue at $200. Save some money for lps.
A used Dynevector 20X HO meaning the high output version it is stupendous. I also owm Heresys but mainly as keepsakes as my first serious audio buy. I understand that there crossover upgrades which even out the sound and make the bass more obvious. I haven't tried it but a lot of people are happy they did.