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.  
128x128oldschool1948
Almost impossible to find, the Signet TK7SU remains the favorite MM cartridge in my collection. 

If you stumble across one, grab it. 
I just received the G with and Ortofon Quintet Black MC cartridge.  The SQ over the 1600 and the Ortofon Blue MM is like WOW!  The Black has so much more detail, music depth, and pure richness.  I'm quite satisfied with my purchases. 

I'm going to let this settle-in and enjoy it for a while, before I jump into my next major room upgrades.  As a next step, I'm trying to decided between a tube preamp or room treatment.  The preamp seems like the next logical step, so that I can "tune" the room to the equipment.  That is, aside from upgraded phono and power cables for the G, which I will do next.