Cartridge upgrade for SME 20/2A???

Okay, it's almost time for a cartridge upgrade for my SME 20/2A (with SME 4.5 arm). Currently I am using a Dynavector 17d mkII and though it sounds pretty good, I'm also pretty sure that the cartridge - along with the phono interconnect - is a limiting factor. Any thoughts that you guys/girls might have would be most appreciated, including information as to the compatability of the SME arm with certain types of cartridges. I'm not even sure of budget yet, though I realize I will have to spend at least double the amount of the 17d mkII to get a real improvement.