what should next upgrade to my analog system be?

I really like my analog system in general so am not looking for suggestions on a complete overhaul and replacing the Lenco idler wheel turntable that I own.

I am debating however whether to upgrade the arm or the cartridge. I bought the turntable used with an existing rega rb-700 arm and shelter 501mkII cartridge. The system really swings! The cartridge will probably need to be retipped in the coming 6 months so the thought occurred to upgrade to the shelter 7000. I was also thinking of perhaps changing the tonearm. I already rewired the tone arm with caras wiring. the turntable is isolated from the table already as well.

As for upgrading the tonearm on a jean natais plinth lenco table, I had heard previously that the Graham phantom b-44 is a good bet. What might I hear more or better going from the rega r700 to the graham. The bass is already deep and yet tight. The soundstage is wide. The sound is warm. Perhaps more midrange? vocals are already amazing. Is the graham with the shelter a good match? My preamp is the dartzeel phono+linestage. I am using a dartzeel amplifier.

thanks

mike
thanks