Cartridge for Technics SL-1200G or SL-1200GR

I've been using a Technics SL-1600MK2 since about 1982.  I'm currently using an Ortofon Blue cartridge.  I have a NAD M12 pre, M22 v2 PA, and Tannoy 8 dcti speakers.

I plan to upgrade to a 1200G or 1200GR and wanted some cartridge recommendations from current owners.  I've considered the Ortofon Black for either, but I'm not sure if that would be overkill for the 1200GR. The Blue sounds pretty good with my current setup, so how much improvement could I expect if I went with the Black.